Billionaires by age: Who got rich how young?

Want to make the Forbes 400 list of the Richest Americans before you're 35? You'd better be good with computers.

Google's Larry Page and Sergey Brin each debuted on the Forbes 400 at the age of 31. Microsoft's Bill Gates broke into the upper echelons of US wealth at 30. And at 27 Apple's Steve Jobs earned a spot on Forbes' first rich list in 1982, although he was already wealthy when Apple went public in 1980. Facebook founder Mark Zuckerberg, the youngest self-made member in the history of the 400, made the list when he was just 24.

Why has the technology industry proven such fertile ground for young moguls?

"It doesn't take a lot of startup capital to start a tech business," says Mark Cuban, who earned a place on the Forbes 400 at the age of 40. "A PC, some smarts and some luck, and the next thing you know ..."

Cuban's model has worked for quite a number of tech prodigies. Steve Jobs cofounded Apple in his family's garage in 1976, with $1,300 cobbled together selling a calculator and a Volkswagen microbus. Apple's current market cap: $239 billion.

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Zuckerberg famously started social networking site Facebook out of his Harvard dorm room in 2004. Although its revenues are kept under wraps, investors have bid as much as $42 per privately held share of Facebook, implying a value of $18.5 billion.

The flip side of this trend is that people tend to get ultra-rich at more advanced ages in businesses that require lots of capital, like real estate, casinos and art.

Wynn Resorts boss Steve Wynn built his Rich List-sized fortune at age 51 after more than two decades in the Las Vegas casino industry. Rival Sheldon Adelson, head of Las Vegas Sands, landed on the list at age 62 after 24 years in the trade show business and the acquisition of his first casino in his mid-50s. A swelling art market pushed collector Norman Braman onto the rich list at age 76.

Image: Microsoft founder Bill Gates broke into the upper echelons of US wealth at 30

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