The Cornish side finished fourth in National League South this season, losing to Maidstone in the play-offs.
"I want to take the club forward into the National League if possible and that's going to take a substantial amount of investment," Masters said.
"If someone wants to come in and take the club in its entirety, that's fine."
Masters, who co-owns Truro with Philip Perryman, says they were putting in £25,000 every month this season to support the club, which is now debt-free.
They took over the club in 2012 when it was on the verge of liquidation and plan to move to a new stadium on the outskirts of the city next year.
"To run a football club and get promotion takes a lot of capital money to get it going, so I would be looking in the region of £500,000-plus," added Masters to BBC Radio Cornwall.
"I've already had a number of people who have been in contact with me in regards to putting investment into the club and one in particular appears to be a good suitor, but the door's open for anyone."
In a statement on Truro's website, Masters has asked potential investors to show their interest by the end of the month and admits the club could suffer without extra funding.
"The club will always survive but we'd seriously have to have a look at ourselves, and that may well mean dropping down a few leagues.
"It's a crossroads but it's not a crisis. At the end of the day there's funding in place for next season and indeed the season after."
Truro City chairman Peter Masters says he is looking for investment of at least £500,000 to help the club reach the National League.