"He made money through what he calls 'criminal mischief,'" revealed GQ's Associate Editor Mickey Rapkin.
The aspiring rap artist opened up about his shady past to the men's magazine, describing how he supported himself as a teenager.
"He delivered pizzas, but also admits he made money through what he calls criminal mischief," Rapkin said. "He appears to be remorseful about the criminal mischief but admits that's where he came from and had to make ends meet."
Rapkin also told us Federline set the record straight about his finances, stating, "I don't rely on my wife's money. I don't get any money from my wife."
So how did K-Fed finagle that sweet Ferrari? "He says that they split his Ferrari 50-50," Rapkin revealed. "But otherwise he doesn't take money from her."
Despite the fancy cars and hip-hop swagger, Kevin openly admitted he's hurting for cash right now.
"Kevin says that he's broke," Rapkin dished. "He made $2 million on the reality show 'Chaotic,' spent $200,000 on an engagement ring for his wife, bought an in-home recording studio and really has spent the rest of the money on the album."
As K-Fed gears up for the fall launch of his debut album on his new label, Federation Records, he's making ends meet with a fashion endorsement deal and making promotional appearances at nightclubs.
Meanwhile, his fourth child, and second baby with Britney, is also due in October.
While Kevin describes his early days with the Princess of Pop as rocky, claiming Britney played hard to get and he nearly walked away, he now jokes that once Mama Spears loses the baby weight, they'll get on stage together and perform.
Catch the rest of Kevin's revealing interview when GQ hits newsstands next week.