It seemed like a perfect match for two buddies who liked nothing better than to have HBO cameras film them playing with stacks of $100 bills in the "24/7" series. But it fell apart when Mayweather got out of prison and decided that he would rather play with his money than invest it in a boxing company.
The requisite Twitter fight ensued, with all the nastiness that comes with any breakup. But that doesn't mean 50 Cent isn't interested in making a real splash in boxing by promoting his former BFF in a fight against, say, Manny Pacquiao.
"I could see myself with the money," the rapper said in an interview with The Associated Press. "And if you've got the money you can make the fight."
That fight could involve more money than any fight ever, with 50 Cent particularly interested in a reported $180 million offer that promoter Bob Arum has from Dubai. But Mayweather has been reluctant to even discuss the possibility of a Pacquiao fight, and 50 Cent thinks he knows why.
One loss, he said, and Mayweather would probably never fight again.
"It's all confidence when it comes to Floyd and his confidence wouldn't be there," 50 Cent said. "He kind of hand picks who he fights instead of taking the tough fights."
Boxing does make strange bedfellows, though there's nothing strange about 50 Cent's foray into the sport. He boxed as an amateur while growing up, and his friendship with Mayweather rekindled a love for the sport.
With Mayweather out, he used his own money to sign several fighters, the most notable being former Cuban Olympic gold medallist Yuriorkis Gamboa. He wants boxing to reclaim the young demographic that it has lost to the UFC, and has plans to mix entertainment with any fights that he promotes.
The rapper, whose real name is Curtis Jackson, was approved last month for a promoter's license in Nevada and is working with Arum's Top Rank on Saturday's fight card that is topped by the fourth fight between Manny Pacquiao and Juan Manuel Marquez.
"We're allies, we're working together," Arum said. "He's really a nice guy. Or at least he seems to be."
But 50 Cent has a learning curve ahead of him, as evidenced by a press conference he was part of Thursday to introduce the undercard that includes Gamboa. When 50 Cent finished a short speech he went to sit down, forgetting to introduce his fighter.
"I (messed) up," he said, laughing.
50 Cent reportedly spent more than $1 million getting the rights to promote Gamboa, a big puncher who he believes will become a big star. The rap mogul likely didn't have to go far for the money, because he made fortunes in both music and in a stake he had in Vitaminwater when it was bought in a 2007 deal by the Coca-Cola company for a reported $4.1 billion.
50 Cent said he wanted to go in the fight business with Mayweather — who made a reported $80 million in his last two fights — not only to make money but to make sure his friend had a continuing source of income after he's done boxing.
Mayweather is famous for a large entourage, sports bets that start at six figures, and throwing money around like he and 50 Cent did in the "24/7" shows.
"He's in the cycle that a lot of big fighters go through," 50 Cent said. "Get the money, spend the money and then fight again for some more money."
50 Cent would like to see his estranged friend do better.
"I still love him," he said. "He's like a brother to me."