"Shark Tank" investor Mark Cuban knew he wanted to be "a business guy" as early as high school, he told podcast host Corby Davidson on an episode of "Your Turn with Corby Davidson."
But he felt limited in the business-related classes he could take at his school: "The only thing they had was an economics class for seniors," the Pittsburgh native said. "They wouldn't let take me it, so I said, 'F--- it, I'm going to see how smart I am,' and went to the University of Pittsburgh at night for my junior year."
He decided to enroll in classes at Pitt and took a bus to and from campus, which was 10 miles from his home, on weeknights.
Cuban did well enough that he figured he could skip his senior year of high school and go straight to college: "I took my college credits from Pitt and my guidance counselor was like, 'OK, we'll work it out,' and they let me graduate using my college credits," Cuban told Davidson.
At 17, he started his freshman year of college at Pitt. "I just wanted to challenge myself," he said.
Cuban decided to transfer after a year because Pitt didn't have an undergraduate business school. He picked Indiana University's Kelley School of Business without ever seeing the campus because it had the cheapest tuition among the top 10 business programs at the time.
The drive that pushed Cuban to finish high school early stuck with him. "I always tried to be different," he told Davidson. And so far, it's served billionaire entrepreneur well.
After graduating from Indiana, he moved back to his hometown and got a job at Mellon Bank, but it wasn't for him. "A lot of my peers at Mellon were just happy to have a job," Cuban wrote in an essay for Forbes. He wasn't: "I wanted to be more entrepreneurial. I took the initiative. I used to send notes to the CEO of the bank. I once cut out a magazine story about how corporations could save money by withholding Social Security and sent it to him. He sent me a thank-you letter back."
He eventually moved to Indiana and then Texas, where he worked for a computer software company. After getting fired for closing a deal without approval from the CEO, Cuban started his own company: MicroSolutions. He went on to sell it to CompuServe for $6 million, which made him a millionaire in his early 30s.
By 40, he'd cofounded another company called Audionet, which became Broadcast.com and was acquired by Yahoo for $5.7 billion. That made Cuban a billionaire at 40.
"Never stop learning. Never stop grinding," he advises young people just starting out their careers. And, "Never stop loving every single minute of your life," he adds.
Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank."
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