There are not a lot of people who get paid to play Tennis.  The only way to become a professional is to compete in tournaments.  Even then, you are not really being paid to play tennis.  It's more likely that the fame you win for competing in those tournaments gets your sponsorship deals with companies that sell things to people who play tennis.  The short answer is compete in local and regional events until you are good enough to compete at the national and international level.  If you are relatively young, plan ahead to attend a college that is known for it's tennis program and talk to the school's athletics association about scholarships.