Mark Cuban is worth over $3 billion today. While that's still far from richest man in the world Bill Gates' net worth of $88 billion, it's still enough to consistently put him in the rankings of the wealthiest people on the planet. More importantly, Cuban started working at age 12 with no family fortune, and nothing but ambition driving him forward. This is his story.

It all began with a pair of shoes. Cuban wanted his father to buy them for him, to which his father said, "If you want new shoes, you'd better find a job." To which little Mark replied, "Dad, I'm twelve, where can I find work?" One of his father's friends gave him some extra garbage bags to try to sell. And so the young business man made his first business, selling the surplus bags door-to-door. Cuban had to work for everything himself, including his college tuition. He made enough to pay for school by giving...dance lessons! We're talking about a very versatile businessman here! After college Cuban went back to his hometown of Pittsburgh (where he was born on July 31st, 1958). There he did something completely different: he started working in IT for Mellon Bank. Following new technologies turned out to be the right step for him, and the beginning of a highly successful career.

Not long after Cuban started his own company selling software. MicroSolutions was later bought by CompuServe for $6 million. He then started an internet radio service called Audionet. Cuban is a huge basketball fan, and the service was first used to tune into Indiana Hoosiers games. Both the name and the purpose of the project were later changed and it became Broadcast.com. Before the IPO, shares of Broadcast.com reached $200. The company was later bought by giant Yahoo! (YHOO  ) for $5.9 million. 

Clearly, Cuban could have stopped there. Yet in 2000, he bought one of the best NBA teams in the world, the Dallas Mavericks. A little over a decade later, they won the NBA championships. Cuban has become a well known figure in American basketball, also running a blog where he offers his thoughts on the NBA. Although his investment in the Mavericks has brought him more riches, he has not stopped investing in other ventures. He was behind the first HD TV channel to hit the market, AXS TV, launched by the company 2929 Entertainment, of which Cuban, of course, is a founder. 

But what does this billionaire do outside of running businesses? Lately he's become a TV star on the popular show Shark Tank, where contestants try to get wealthy entrepreneurs to invest in their ideas. He has also become an outspoken critic of President Donald Trump, who he first promised to give a shot as President, and has since decided is not worth supporting. Cuban thinks President Trump has neither the empathy nor the interest in the world to be a good leader. Since both men are known for their bluntness and occasionally bad language, it could be a case of "it takes one to know one." We'll let them have the last word on this one.