Making Mint By helping people manage their money, this entrepreneur is earning his.

Wherever money is transacted, tracked or traded, there is a profit to be made. It's a fundamental principle of markets from Wall Street to eBay. Now Web 2.0 entrepreneur Aaron Patzer, 27, is putting that principle to work. Patzer was tired of spending hours at his PC entering expense details into financial programs like Quicken. That's when he created Mint, an online application that tells you how you're spending your money by instantly aggregating financial information from your online bank and credit card accounts.

Although the service is free for the site's 430,000 users, there are several hooks in place to ensure that Mint will make a mint for Patzer and his investors. Primarily, since Mint knows where you bank and how you spend, the site engages in suggestive upselling, nudging users toward banking and brokerage partners, or suggesting new mortgages and credit cards.

As for advertising revenue, Mint sells quality over quantity: Since the service already knows where you shop and what you buy, ads are more targeted--and more profitable. "The only ads you'll ever see on Mint are those calculated to save [the user] at least $50," says Patzer, who's already raised $17 million in funding for his Mountain View, California-based company. "We'll soon offer cash back and coupons for the places you shop most often."