Young Millionaires 2010Here's how four ultra-successful twentysomethings leveraged their brilliant ideas into major businesses online. And how you can, too.

Out of Her Closet, a $50 Million Business
Susan Gregg was 17 and heading off to Carnegie Mellon University, and she had a problem: a closet overstuffed with one-of-a-kind vintage shoes and dresses. The solution? Open an online boutique.

ModCloth.comwas headquartered in her dorm room and run with the help of her high school sweetheart, Eric Koger. The two drove from Pittsburgh to their South Florida hometown several times throughout college to haul up stock. By the end of their senior year in 2006, ModCloth was getting 60,000 visitors a month, and plenty of them were asking for more.