Tesla and SpaceX CEO Elon Musk may not have had a lot of money in college, but he always had an entrepreneurial spirit, even when it came to paying rent.
In 1989, Musk left South Africa to attend Queen's University in Ontario, Canada. After spending two years in Ontario, he transferred to the University of Pennsylvania on scholarship in 1992.
There, Musk and his roommate, Adeo Ressi, rented a large, relatively cheap frat house off campus. The roomates transformed the 10-bedroom home into a nightclub, according to "Elon Musk: Tesla, SpaceX, and the Quest for a Fantastic Future" by Ashlee Vance, and they used it to generate money to pay rent.
"I was paying my own way through college and could make an entire month's rent in one night," Musk said in the book. "Adeo was in charge of doing cool s--t around the house, and I would run the party."
Ressi described the parties as "a full-out, unlicensed speakeasy" in the book.
"We would have as many as 500 people," Ressi said. "We would charge five dollars, and it would be pretty much all you could drink— beer and Jello shots and other things."
But Musk wasn't a big drinker, according to Vance, and aside from the occasional vodka and Diet Coke, he did not care for the taste of alcohol. "Somebody had to stay sober during these parties," Musk said in the book.
Ressi also described Musk as "the most straight-laced dude... he never drank. He never did anything. Zero. Literally nothing."
Musk often didn't even hang around to party.
"There where some nights where I'd be like, 'Where's Elon?' and I'd go up to his room and pound on the door and he's in there alone playing a video game," Ressi said Vance's book.
The only time Ressi felt he had to moderate Musk's behavior was during his video game binges that would last days, according to the book, when Ressi would have to make him stop playing.
A representative for Musk did not immediately respond to CNBC Make It's request for comment.