TMZ Sports is told Mayweather has inked a massive, $402 million real estate deal to buy more than 60 buildings in New York City ... totaling more than 1,000 units around the Big Apple.

"Growing up I used to dream about owning just one home by myself, when you work hard you can achieve anything," Mayweather told us after agreeing to the deal, and sending a huge chunk of change to the sellers.

47-year-old Mayweather is buying the properties, mostly located in upper Manhattan, from Black Spruce Management, according to the Real Deal.

We're told Floyd is aiming to provide affordable housing to families who are struggling to get by.

Of course, Floyd was one of the greatest pugilists to ever step into the squared circle, retiring with a 50-0 record after defeating Conor McGregor in August 2017.

Mayweather made BANK for the fight ... raking in hundreds of millions of dollars alone for the 10-round fight. Rinse and repeat for the Manny Pacquaio fight two years earlier.

Over the years, TBE's come back from time to time to fight in exhibition matches -- the last being John Gotti III -- and that's caused some people to speculate Floyd's having money troubles.