An entrepreneur at heart, at a young age Mark Cuban began selling stamps door-to-door and gave disco lessons to help pay his way through Indiana University. Cuban was inspired to strike out on his own when he was fired from a software shop for closing a $15,000 sale instead of cleaning up the store. In 1995, Cuban founded video portal Broadcast.com with fellow Indiana University alum, Todd Wagner. Four years later, he sold Broadcast.com to Yahoo for $5.7 billion. Today he owns the NBA's Dallas Mavericks and has stakes in Magnolia Pictures, AXS TV, and dozens of small startups. Cuban invests in mission-driven companies such as Luminaid, which provides lighting to disaster areas, and Mahmee, a maternal healthcare tech company. He is also well known as being an investor on the Emmy award winning show, Shark Tank.