His first job was tending bar in Dallas. Then he took a gig as a computer salesman. He was fired - and he realized he "$4."
So he started his first company, MicroSolutions, which he sold for $6 million.
He did even better with his next company - about 1,000 times better. He founded Broadcast.com and sold it to Yahoo for almost $6 billion.
Almost immediately, Cuban sold all of his Yahoo stock netting $2 billion in cash for himself. Weeks later, the market crashed.
Since then, Cuban has continued to work and invest. He owns the Dallas Mavericks and $4, plus he's all over the media - taking bites out of would-be entrepreneurs on ABC's pitch show "Shark Tank" and lighting up the conference circuit.
Cuban is known for saying what other people only think. Here are some of our favorite quotes.