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."