John Urschel had a short but lucrative, NFL career. The offensive lineman, who retired at age 26 in 2017 to pursue his PhD at MIT, earned $1.8 million over his three seasons with the Baltimore Ravens. His salary was as high as $600,000 in 2016, but Urschel never lived like he was making six figures. In fact, he did the opposite. "I drive a used hatchback Nissan Versa and live on less than $25,000 a year," the athlete wrote on The Players' Tribune in 2015.

Urschel bought the Nissan after he was drafted by the Ravens in 2014. It cost him $9,000, just a fraction of his $144,560 signing bonus. Even his mom has joked about the Versa, which had 30,000 miles on it when Urschel bought it:

It's his "dream car," he told ESPN in 2015. "It's great on gas. It's surprisingly spacious. And you know what the best feeling is? You're driving into a parking deck, it's near full and you're on the first level and there is that space that everyone has passed because they said, 'No, we can't park in there.' And I take my Versa and I just go right in there." He didn't live on a modest $25,000 a year and drive a used car "because I'm frugal or trying to save for some big purchase," Urschel noted. "It's because the things I love the most in this world (reading math, doing research, playing chess) are very, very inexpensive."

Former NFL player John Urschel Matt Hazlett | Getty Images

Urschel not only loves math, he's quite good at it. He earned a bachelor's and master's in mathematics while maintaining a 4.0 GPA and his work has been published in numerous journals, including the Journal of Computation Mathematics and the SIAM Journal of Numerical Analysis.

The things I love the most in this world (reading math, doing research, playing chess) are very, very inexpensive. John Urschel former NFL player and current PhD student