'Forbes' just released its annual list of the world's richest people and there's a new person on the list who proves two things.

One, you NEVER know what will be a billion-dollar idea. And two, there's a FORTUNE in figuring out ways to slim people down without making them eat vegetables or do actual exercise.

41-year-old Sara Blakely of Clearwater, Florida is the founder of SPANX. If you're not familiar, Spanx are spandex-type wraps you wear under your clothes to slim you down and smooth out your bulges.

Here's a commercial for Spanx that may explain them a little better:

And because she invented them, Sara's now the youngest self-made female BILLIONAIRE in the world. There are female billionaires who are younger, but they inherited their money.

Sara started Spanx in the late '90s, when she came up with the idea at age 27. She used all $5,000 she had in the bank to start the company. The product caught on and now, she has a net worth of $1 BILLION.

One more note: Sara would never have started Spanx if she'd gotten the first job she applied for...playing Goofy at Disney World. They rejected her because you have to be 5-foot-8...and she's 5-foot-6.

(Tampa Bay Times)

Here's Sara with some tips for aspiring billionaires: