user20657: I have played chess since a very young age and my tactics are very developed in my opinion. However, I never bothered to read chess related books about opening or related theory. This often leads to interesting games as I don't follow well known openings which throws off my opponents. Would it be a good idea for me to enter a tournament with an entry fee in the hopes of winning prize money? Or would I get completely crushed by my opponents? I am roughly a 1900 ELO rated player - checked online.

user657: First of all, don't trust the online ratings. I've been rated by various digital arenas as much as 600 points more than my "real" rating. There's an inherent variability in rating systems, such that even two systems based on the exact same equations can come up with divergent ratings for the same player. (Elo, the man the international rating system is named for, described rating chessplayers as trying to measure the depth of a rapidly moving stream with a yardstick suspended from a Willow branch in the wind. There's too many variables to do it accurately.)
That having been said, go ahead and play tournament chess. Opening theory is overrated when your opponents are rated under 2000, maybe even 2200. A good feel for the game will serve you better than a dozen opening books. I can't tell you how many times I've emerged from the opening with the worse game, only to win in the end. Go, play, and enjoy.
Just be prepared for reality to give you a cold, hard, slap in the face. Decades ago, when I started playing in organized events, I discovered a completely new world. I'd won most every game I'd played up until that point; it took 4 tournaments to win my second game. Not saying this will happen to you, just warning you to be prepared to handle it if it does.
But here's a definite advisory: the good tournament players will not be put off by deviations from opening theory; only the ones whose opening preparation consists solely of memorization. Bent Larsen once observed that a player that has memorized the moves will win more than one who hasn't, but the player who understands the position will win more than both of them. In any mid-size or larger, non-scholastic, tournament you will find a good proportion of those.
Tactical strength is the foundation of chess; don't mistake it for the whole edifice.

user18738: play because chess is fun. You will lose more money than you gain in chess unless you are very strong.

user20721: No.  
Entering tournaments to make money is a fools errand.   
There is much cheating that occurs in them.  And plenty of us 1900 players  (real 1900 federation rated not the fake online ratings) also deviate from the book to befuddle those who only know the book and think that the book is always right.
And since we do know theory and have good tactics too you will be surprised at  your results if you play actual rated 1900 players.  

user20776: What chess theory?  How much theory?
Back when I started playing in tournaments there was very little material to help learn "theory".   What passed for theory was very basic information and simple problems.  Underpromoting to a horsie was the hardest I recall.  Good books on tactics would have helped but I did not have any of those. 
Later I found a copy of a book on openings which was interesting but not that useful except in postal chess. 
I am not sure how I developed my skills but it may have mostly just been by playing tournaments.  Some was reading anything I could find to help learn more principles which might be called theory.  I did find a book on endings which I devoured and that definitely helped. Openings were very basic and I used ability with tactics to get my way through them and usually get a better game. 
Anyway like @Edwina Oliver noted above, and others had similar sentiments,  you will not make money playing in tournaments.  It is a zero sum game. You make money by being so good that they pay you to show up and compete for prizes. 
I knew one kid who had won money in his first very small club tournament.  He then figured he would always be making money so he started playing in more tourneys.  The next one I saw he was complaining that he did not make anything at all because the prize for second/third had been split between two players tied for second  and he though since he was third in numerical scores  he should have gotten the third place money even though he was 4th in people scoring. There were only 3 prizes and about ten people in the event.
Do you need theory to play and do well.  No.
Will you need some theory to play better.  yes.
And will you make money playing in tournaments.  Not until you are a tippy top GM.  GMs are a dime a dozen.  I see them playing in every medium sized tournament trying to make a living.  

user17425: I was 18, and never played in a tournament so was unrated.  As a new player I could have played in a low division and won a prize.  I played in the open division and got to play against local champions.  Seeing how I did against the best was one of my primary goals.  I learned a lot.  
What I didn't expect was an introduction to chess culture.  They way folks reviewed games, the nightly blitz battles, all those chess books was new to me.  The gathering around an interesting game. Have fun!

user15509: If you've never played OTB tournaments, don't be misguided by your online rating. I had about 1700 online rating when I entered my first tournament: I was crushed losing to 1300 and even to 1100's. Tournament play is a different beast, with more time think expect a lot better quality play from the opposition than what you are used to seeing. Money or not, you should definitely play, it's totally amazing.

user18020: As a partial answer that I started as a comment to the (now-accepted) answer: Prepare yourself mentally that you may lose against somebody much weaker, purely due to the stress of the new.  When walking up to a tournament area --- whether game table, dojo, ring, field, or other, --- you find out how you deal with that stress... 
Just having to write down your moves on paper may fluster you, throwing off the rest of your composure & then you start thinking about what the spectators and opponent is thinking, you don't lose focus so much as focus on the wrong things. And then maybe the second or third game, all falls in place; you still have almost the same adrenalin shot but you find it clears your head.  
Or on the other hand, you may find yourself completely in your element, a natural at competing, beating superior but less stress-resistant opponents! 
But this in itself is a value to competing: learning how you deal with such stress, and then learning to better deal with it; the benefits of this clearly extend to other situations (inspections, management at work, courtroom appearances, ... ), and may inform you if you should search or avoid such situations. 
Your mileage may vary. But the tournament prize money is (beyond practical considerations like repaying fees and costs) irrelevant, 'peanuts' to the non-financial benefits in the various answers given.

user19877: You should play because you want to play, not for the money.
At 1900, you might win some money here or there, but it will not be a lot, and will likely only offset your costs just a little as you are much more likely to spend more on entry fees, books, online subscriptions, etc. There is a lot of competition at any level, so you may win some money sometimes, and not other times. Also, be aware that 1900 online is not usually close to 1900 in over-the-board play, and may be off by 200 points, or more.
It also takes a while to get used to playing in tournaments, and that experience cannot be discounted. When I first started playing, the stress before each game would get me sick. Over time, I overcame that, but that is one example, and it is something that you need to get over with experience.
As far as not knowing theory, you are talking to someone, who hates theory. I got to 2298 knowing very little except how to play opening pawn structures. Understanding what you should be trying to achieve is more important than knowing exact moves that you do not understand, especially when your opponent is not going to follow book for 30 moves. 
Learning about opening pawn structures, and the pawn breaks associated with them, can be learned in the following books:

“Complete Chess Strategy” volumes 1,2 and 3 by Ludek Pachman. (This teaches about many basic plans, and what you are striving for with your pieces and pawns, especially. THIS is what made me a master.)
“Pawn Structure Chess” by Andy Soltis. (This extends the above to specific opening structures.)
“Chess Structures: A Grandmaster Guide” by Mauricio Flores Rios (This is an extension of “Pawn Structure Chess”, and is deeper, and covers more structures. It is outstanding especially if you have already covered “Complete Chess Strategy”.)

Here is a good link with some basics.
In any case, good luck with your first tournament.

user4418: 
Would it be a good idea for me to enter a tournament with an entry
  fee?

Absolutely! Playing over-the-board chess tournaments is a lot of fun. There is social interaction which is almost completely absent in online play and it will be good for you to compare your level of play with other players in "real" chess. You can also learn a lot in post-game discussions with your opponents.

in the hopes of winning prize money?

"Hope" is good. 
"Expectation" could be misplaced. I'm afraid there is a word which comes up in the chess world - "sandbagging". If there are sandbaggers in the tournament you enter then you won't win money. You hope you pick a tournament with none of these players and you might be in with a chance. 
An example of something which looks suspiciously like this activity is available here. In one month the player gained 72 rating points by scoring 5.5/7 against players with an average rating of 1947 in a tournament with generous prize money and also managed to lose 91 rating points in another tournament by losing 5 games in a row against players with an average rating below 1385 (3 players had ratings more than 400 points below the player's rating and so their ratings were rounded up to be just 400 points below).
Juniors or very young players are also a (more legitimate) danger to your hopes of winning money. The problem there is that they are often improving very rapidly and their rating lags a long way behind their playing level.
Thirdly, you are unrated yourself. Many tournaments which have rating limits (you must be below a certain level to enter) will allow you to enter but not win a prize.

user14079: There is nothing wrong in entering a tournament if you have the time and if you can afford the entry fee.
However, I think you should really consider your first tournament as a discovery experience and enjoy the pleasure of chess and the atmosphere of the tournament rather than worry at once about winning prize money.
Whether you can win something depends a lot on the specifics of the tournament, the field, and of course your own level. I wouldn't put too much faith in online estimates of your strength: real-life chess is quite different. Playing your first tournament will actually give you a much better evaluation of where you stand vis-à-vis competition chess, and the experience will probably make you pretty stronger for your second one!
In a typical Swiss-system open tournament, you won't get crushed in all your games: whether your 1900-elo online estimation translates to real-chess 1900, or 1700, or 1500, there are many players of every level entering such events, and there will almost certainly be some opponents that you can beat. Probably you will get crushed in a few games, but not throughout the tournament, and you will have your revenge in others.
Some tournaments have prize money for unrated players. This may be a nice plus at the end, or a goal to aim for if your are well-placed before the last couple of games. But don't worry about it at the starting line, concentrate on your chessboard!
Finally, studying chess, reading books or training is up to you. It certainly doesn't hurt to play over some grandmaster's games collection, for instance. In any case, don't overestimate the importance of opening theory: it does help, but you wouldn't be the first tournament player to reach decent results without delving into it. 
Welcome in the world of competitive chess and have a nice tournament!

20657: <p>I have played chess since a very young age and my tactics are very developed in my opinion. However, I never bothered to read chess related books about opening or related theory. This often leads to interesting games as I don't follow well known openings which throws off my opponents. Would it be a good idea for me to enter a tournament with an entry fee in the hopes of winning prize money? Or would I get completely crushed by my opponents? I am roughly a 1900 ELO rated player - checked online.</p>
 657: <p>First of all, don't trust the online ratings. I've been rated by various digital arenas as much as 600 points more than my "real" rating. There's an inherent variability in rating systems, such that even two systems based on the exact same equations can come up with divergent ratings for the same player. (Elo, the man the international rating system is named for, described rating chessplayers as trying to measure the depth of a rapidly moving stream with a yardstick suspended from a Willow branch in the wind. There's too many variables to do it accurately.)</p>

<p>That having been said, go ahead and play tournament chess. Opening theory is overrated when your opponents are rated under 2000, maybe even 2200. A good feel for the game will serve you better than a dozen opening books. I can't tell you how many times I've emerged from the opening with the worse game, only to win in the end. Go, play, and enjoy.</p>

<p>Just be prepared for reality to give you a cold, hard, slap in the face. Decades ago, when I started playing in organized events, I discovered a completely new world. I'd won most every game I'd played up until that point; it took 4 tournaments to win my second game. Not saying this will happen to you, just warning you to be prepared to handle it if it does.</p>

<p>But here's a definite advisory: the good tournament players will not be put off by deviations from opening theory; only the ones whose opening preparation consists solely of memorization. Bent Larsen once observed that a player that has memorized the moves will win more than one who hasn't, but the player who understands the position will win more than both of them. In any mid-size or larger, non-scholastic, tournament you will find a good proportion of those.</p>

<p>Tactical strength is the foundation of chess; don't mistake it for the whole edifice.</p>
 18738: <p>play because chess is fun. You will lose more money than you gain in chess unless you are very strong.</p>
 20721: <p>No.  </p>

<p>Entering tournaments to make money is a fools errand.   </p>

<p>There is much cheating that occurs in them.  And plenty of us 1900 players  (real 1900 federation rated not the fake online ratings) also deviate from the book to befuddle those who only know the book and think that the book is always right.</p>

<p>And since we do know theory and have good tactics too you will be surprised at  your results if you play actual rated 1900 players.  </p>
 20776: <p>What chess theory?  How much theory?</p>

<p>Back when I started playing in tournaments there was very little material to help learn "theory".   What passed for theory was very basic information and simple problems.  Underpromoting to a horsie was the hardest I recall.  Good books on tactics would have helped but I did not have any of those. </p>

<p>Later I found a copy of a book on openings which was interesting but not that useful except in postal chess. </p>

<p>I am not sure how I developed my skills but it may have mostly just been by playing tournaments.  Some was reading anything I could find to help learn more principles which might be called theory.  I did find a book on endings which I devoured and that definitely helped. Openings were very basic and I used ability with tactics to get my way through them and usually get a better game. </p>

<p>Anyway like @Edwina Oliver noted above, and others had similar sentiments,  you will not make money playing in tournaments.  It is a zero sum game. You make money by being so good that they pay you to show up and compete for prizes. </p>

<p>I knew one kid who had won money in his first very small club tournament.  He then figured he would always be making money so he started playing in more tourneys.  The next one I saw he was complaining that he did not make anything at all because the prize for second/third had been split between two players tied for second  and he though since he was third in numerical scores  he should have gotten the third place money even though he was 4th in people scoring. There were only 3 prizes and about ten people in the event.</p>

<p>Do you need theory to play and do well.  No.
Will you need some theory to play better.  yes.
And will you make money playing in tournaments.  Not until you are a tippy top GM.  GMs are a dime a dozen.  I see them playing in every medium sized tournament trying to make a living.  </p>
 17425: <p>I was 18, and never played in a tournament so was unrated.  As a new player I could have played in a low division and won a prize.  I played in the open division and got to play against local champions.  Seeing how I did against the best was one of my primary goals.  I learned a lot.  </p>

<p>What I didn't expect was an introduction to chess culture.  They way folks reviewed games, the nightly blitz battles, all those chess books was new to me.  The gathering around an interesting game. Have fun!</p>
 15509: <p>If you've never played OTB tournaments, don't be misguided by your online rating. I had about 1700 online rating when I entered my first tournament: I was crushed losing to 1300 and even to 1100's. Tournament play is a different beast, with more time think expect a lot better quality play from the opposition than what you are used to seeing. Money or not, you should definitely play, it's totally amazing.</p>
 18020: <p>As a partial answer that I started as a comment to the (now-accepted) answer: Prepare yourself mentally that you may lose against somebody much weaker, purely due to the stress of the new.  When walking up to a tournament area --- whether game table, dojo, ring, field, or other, --- you find out how you deal with that stress... </p>

<p>Just having to write down your moves on paper may fluster you, throwing off the rest of your composure &amp; then you start thinking about what the spectators and opponent is thinking, you don't lose focus so much as focus on the wrong things. And then maybe the second or third game, all falls in place; you still have almost the same adrenalin shot but you find it clears your head.  </p>

<p>Or on the other hand, you may find yourself completely in your element, a natural at competing, beating superior but less stress-resistant opponents! </p>

<p>But this in itself is a value to competing: learning how you deal with such stress, and then learning to better deal with it; the benefits of this clearly extend to other situations (inspections, management at work, courtroom appearances, ... ), and may inform you if you should search or avoid such situations. </p>

<p>Your mileage may vary. But the tournament prize money is (beyond practical considerations like repaying fees and costs) irrelevant, 'peanuts' to the non-financial benefits in the various answers given.</p>
 19877: <p>You should play because you want to play, not for the money.</p>

<p>At 1900, you might win some money here or there, but it will not be a lot, and will likely only offset your costs just a little as you are much more likely to spend more on entry fees, books, online subscriptions, etc. There is a lot of competition at any level, so you may win some money sometimes, and not other times. Also, be aware that 1900 online is not usually close to 1900 in over-the-board play, and may be off by 200 points, or more.</p>

<p>It also takes a while to get used to playing in tournaments, and that experience cannot be discounted. When I first started playing, the stress before each game would get me sick. Over time, I overcame that, but that is one example, and it is something that you need to get over with experience.</p>

<p>As far as not knowing theory, you are talking to someone, who hates theory. I got to 2298 knowing very little except how to play opening pawn structures. Understanding what you should be trying to achieve is more important than knowing exact moves that you do not understand, especially when your opponent is not going to follow book for 30 moves. </p>

<p>Learning about opening pawn structures, and the pawn breaks associated with them, can be learned in the following books:</p>

<ol>
<li>“<em>Complete Chess Strategy</em>” volumes 1,2 and 3 by Ludek Pachman. (This teaches about many basic plans, and what you are striving for with your pieces and pawns, especially. THIS is what made me a master.)</li>
<li>“<em>Pawn Structure Chess</em>” by Andy Soltis. (This extends the above to specific opening structures.)</li>
<li>“<em>Chess Structures: A Grandmaster Guide</em>” by Mauricio Flores Rios (This is an extension of “Pawn Structure Chess”, and is deeper, and covers more structures. It is outstanding especially if you have already covered “<em>Complete Chess Strategy</em>”.)</li>
</ol>

<p><a href="https://chess.stackexchange.com/questions/26906/opening-moves-pawn-chains-and-countering-attacks/26910#26910">Here is a good link with some basics.</a></p>

<p>In any case, good luck with your first tournament.</p>
 4418: <blockquote>
  <p>Would it be a good idea for me to enter a tournament with an entry
  fee?</p>
</blockquote>

<p>Absolutely! Playing over-the-board chess tournaments is a lot of fun. There is social interaction which is almost completely absent in online play and it will be good for you to compare your level of play with other players in "real" chess. You can also learn a lot in post-game discussions with your opponents.</p>

<blockquote>
  <p>in the hopes of winning prize money?</p>
</blockquote>

<p>"Hope" is good. </p>

<p>"Expectation" could be misplaced. I'm afraid there is a word which comes up in the chess world - "sandbagging". If there are sandbaggers in the tournament you enter then you won't win money. You hope you pick a tournament with none of these players and you might be in with a chance. </p>

<p>An example of something which looks suspiciously like this activity is available <a href="https://ratings.fide.com/individual_calculations.phtml?idnumber=1250043&amp;rating_period=2017-11-01&amp;t=0" rel="noreferrer">here</a>. In one month the player gained 72 rating points by scoring 5.5/7 against players with an average rating of 1947 in a tournament with generous prize money and also managed to lose 91 rating points in another tournament by losing 5 games in a row against players with an average rating below 1385 (3 players had ratings more than 400 points below the player's rating and so their ratings were rounded up to be just 400 points below).</p>

<p>Juniors or very young players are also a (more legitimate) danger to your hopes of winning money. The problem there is that they are often improving very rapidly and their rating lags a long way behind their playing level.</p>

<p>Thirdly, you are unrated yourself. Many tournaments which have rating limits (you must be below a certain level to enter) will allow you to enter but not win a prize.</p>
 14079: <p>There is nothing wrong in entering a tournament if you have the time and if you can afford the entry fee.</p>

<p>However, I think you should really consider your first tournament as a discovery experience and enjoy the pleasure of chess and the atmosphere of the tournament rather than worry at once about winning prize money.</p>

<p>Whether you can win something depends a lot on the specifics of the tournament, the field, and of course your own level. I wouldn't put too much faith in online estimates of your strength: real-life chess is quite different. Playing your first tournament will actually give you a much better evaluation of where you stand vis-à-vis competition chess, and the experience will probably make you pretty stronger for your second one!</p>

<p>In a typical Swiss-system open tournament, you won't get crushed in all your games: whether your 1900-elo online estimation translates to real-chess 1900, or 1700, or 1500, there are many players of every level entering such events, and there will almost certainly be some opponents that you can beat. Probably you will get crushed in a few games, but not throughout the tournament, and you will have your revenge in others.</p>

<p>Some tournaments have prize money for unrated players. This may be a nice plus at the end, or a goal to aim for if your are well-placed before the last couple of games. But don't worry about it at the starting line, concentrate on your chessboard!</p>

<p>Finally, studying chess, reading books or training is up to you. It certainly doesn't hurt to play over some grandmaster's games collection, for instance. In any case, don't overestimate the importance of opening theory: it does help, but you wouldn't be the first tournament player to reach decent results without delving into it. </p>

<p>Welcome in the world of competitive chess and have a nice tournament!</p>
