Investing.com - Most of us know Elon Musk as the eccentric billionaire who makes electric cars and wants to send humans to mars. But who is Elon Musk, and how did he become the successful businessman is he today?Musk was born in 1971 in South Africa. At 24, he deferred his admission to study for his PhD to try his luck at a software company. With his brother Kimbal and 28,000 dollars from their father, he launched Zip2, a company that provided online city guides to newspapers. Four years later, in 1999, Compaq bought Zip2 for $307 million, netting Elon 22 million dollars.Many would have stopped there, but Musk used 10 million of the Zip2 sale to found X.com – an online banking company. X.com was merged with Confinity a year later, forming what we now know as PayPal. Musk was named CEO but was fired shortly after. As PayPal's biggest shareholder he still banked on PayPal's sale to eBay in 2002, making 165 million from the sale.2002 was also the year SpaceX was born, but the Space Company struggled for 6 years before successfully launching their fourth Falcon 1 rocket. Since then, SpaceX secured multiple contracts with NASA.Tesla (NASDAQ:TSLA), the endeavor for which Musk is probably best known, was founded in 2004. Tesla was off to a rocky start and needed constant influxes of new money to keep going. Elon himself invested over 70 million dollars from his own money to save Tesla. Musk took Tesla public in 2010, raising an additional 226 million for the company. Since then came the Model S, X, and most recently – the Model 3. Maybe more importantly, Tesla is now the second most valuable US car manufacturer, right after GM, and before Ford.Musk has never been afraid to dream big, and put his money where his mouth is. Today, his worth is estimated at 21 billion dollars. Not a bad return on the 28 thousand he and his brother started with in 1995.