After graduating from Penn, Musk was going to get thrown out of the country unless he got himself sorted out. So he did what anybody does in that situation — he studied applied physics at Stanford.

But he soon realized that the academic life wasn't what he wanted.

"It got to the start of the quarter at Stanford, so I had to make a decision, and I decided to go on deferment," he tells Foundation. "I figured if I start a company and it doesn't work, then I can always go back and graduate school. So I talked to the chairman of the department and he let me go on deferment. I said I'd probably be back in six months, and he said he was probably never going to hear from me again. And he was correct. I've never spoken to him since."

Musk joined up with his brother Kimbal and Greg Kouri, a mutual friend who has since died.

They began Zip2, a startup that helped provide online publishing for Knight-Ridder and other print publications.

"The initial idea was to create software that would help bring the media companies online," he says. "So we helped, in a small way, bring companies like The New York Times, and so forth, online. They weren't always online; people don't realize that."

Zip2 sold to AltaVista for $307 million in 1999.

Suddenly, Musk was rich.

Musk got rich with the Zip2 acquisition.

But he wanted to have a bigger impact.

So he started in on another idea: taking financial services online in ways that banks wouldn't imagine possible.

"The banks are terrible at innovation, and financial services is a huge sector, so I thought, 'There should be something here,'" he tells Inc.

The idea resonated. Sequoia Capital led a $25 million dollar investment round on X.com.

As 1999 wore on, Musk reoriented X.com to doing strictly online payments.

This put him in direct competition with Confinity, a company run by Peter Thiel and Max Levchin. When Confinity released its PayPal product in late 1999, Musk was coming for them.

As Thiel — now a billionaire investor — writes in his new book "Zero to One":

X's product mirrored ours feature-for-feature. By late 1999, we were in all-out war. Many of us at PayPal logged 100-hour workweeks...

But in February 2000, Elon and I were more scared about the rapidly inflating tech bubble than we were about each other: a financial crash would ruin us both before we could finish our fight.

So in early March we met on neutral ground ... and negotiated a 50-50 merger.

With their teams combined, Thiel and Musk were able to survive the dot-com crash and build a successful business — eventually going public and getting acquired by Ebay for $1.5 billion.

When a friend asked Musk what he would do after PayPal, he said that he was always interested in space, but he didn't know how to get there.

"So I went to the NASA website to see when we were going to Mars," he said during a SXSW talk, "and I couldn't find that out. I thought maybe it was there, but well hidden or something."

His goal: to put a greenhouse on Mars. But he'd need a vehicle.

He went shopping in Russia.

"I went to Russia three times to try to buy a couple of their biggest ICBMs," Musk said. "It was an interesting experience. I sort of got the feeling I could have bought the nuke, too, but I didn't want to go there."

But there was one problem. He couldn't figure out the rockets.

"I was clueless," he said. "I had no idea what the heck I was doing."

A lifelong autodidact, Musk taught himself rocket science. And by hiring the best in the astronomical business, he got SpaceX off the ground.

In 2001, Musk gave a talk at Stanford about how humans could possibly deal with gravity on the planet Mars.

Struck by the clarity of his ideas, Martin Eberhard and Marc Tarpenning introduced themselves after his talk.

Three years later, they wrote to Musk about the fast, efficient electric car they were developing at their startup, Tesla Motors.

He took a meeting with them. With a few days convincing, he decided to lead the first round of financing. Musk would supply much of the coffers in Tesla's fraught first few years, pouring in his "last $35 million" of cash.

Not content with electric cars and space exploration, Musk decided to get into solar power, too.

In 2004, he was in an RV driving to Burning Man with his cousin Lyndon Rive.

"You should look into solar," Musk told his cousin.

It's turned into a $5 billion business.

Unlike with PayPal, Tesla, or SpaceX, Musk doesn't run SolarCity, but its goals are characteristically ambitious.

"Our intent is to combine what we believe is fundamentally the best photovoltaic technology with massive economies of scale to achieve a breakthrough in the cost of solar power," they wrote in a blog post.

Eberhard and Musk had a constructive — and contentious — relationship from the start.

But by the end of 2007, the relationship reached a tipping point. Eberhard got fired.

So did the transition CEO Michael Marks. And the follow-up CEO Ze'ev Drori.

In October 2008, Musk stepped in as Tesla's chief executive.

He had invested $55 million of his own money into the company.

"I've got so many chips on the table with Tesla," he told the New York Times, "it just made sense for me to have both hands on the wheel."

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