Despite raking in millions, many professional athletes choose to live like they're broke by driving cheap cars or moving in with their parents. Others realize too late that they've done themselves in with reckless spending. Here's what four successful NBA stars say are their biggest money regrets and what they learned from them.

Shaquille O'Neal blew through $1 million in an hour

In 1992, a 20-year-old Shaquille O'Neal signed his first professional contract, officially becoming a millionaire. But within an hour, the budding basketball star had already gone on an expensive shopping spree and was down over $1 million. O'Neal's first purchase: a $150,000 Mercedes Benz for himself. He immediately followed that up with a matching one for his father and a smaller $100,000 one for his mother. O'Neal also paid off his mother's house and began doing "what all the homeboys do — gotta buy rings and diamonds and earrings and this and that," he told Business Insider. A few days later, O'Neal's bank manager explained that he was already $60,000 underwater. That served as the wake-up call O'Neal needed to become more careful and get his spending on track. However, he doesn't regret helping out his parents. "I [spent] a million dollars in about 45 minutes," he told CNN. At least in part, though, "it was well worth it."

Ben Simmons spent $10,000 on two Savannah cats

As the No. 1 overall pick in the 2016 NBA draft, Ben Simmons signed a $18.5 million contract with the Philadelphia 76ers, putting his average annual salary at about $6.17 million. The basketball star signed a lucrative sneaker deal with Nike on top of that. But after becoming a millionaire virtually overnight, Simmons fumbled a few of his earliest purchases. On a recent episode of "Kneading Dough," Simmons told Maverick Carter that his biggest regrets were buying two Savannah cats, which cost a combined $10,000. "It was a bad purchase," he said. The 21-year-old no longer owns the cats, who proved too unruly for him to handle. "They got crazy," he said. "One made the other one crazier."

Antoine Walker lost $100 million and had to file for bankruptcy

Three-time NBA All-Star Antoine Walker made more than $108 million over a 12-year career in the league. But just two years after retiring from basketball, he'd lost it all and had to file for bankruptcy when he found himself more than $12 million in debt. His over-the-top spending combined with gambling losses and real estate investments that tanked in 2007 left him with nothing. The incident forced Walker to take a new perspective on spending, and he has since made it his life's mission to educate others about financial responsibility. Walker is now a consultant for the Morgan Stanley Global Sports & Entertainment financial literacy initiative, which educates college and professional athletes on money management.

Draymond Green spent $21,000 on one night at a club