By 25, Cuban had graduated from Indiana University and had moved to Dallas. The "Shark Tank" investor started out as a bartender and then worked as a salesman for a PC-software retailer. He got fired because he wanted to go close a deal rather than open a store in the morning. That helped inspire him to open his first business, MicroSolutions.

"When I got to Dallas, I was struggling — sleeping on the floor with six guys in a three-bedroom apartment," Cuban writes in his book "How to Win at the Sport of Business." "I used to drive around, look at the big houses, and imagine what it would be like to live there and use that as motivation."