Whatevercash.com.....How a 15-year-old's hobby became a $50,000-to-$70,000-a-month business.

Girls between the ages of 12 and 19 have an estimated $87 billion in buying power, according to market research firm TRU, and Ashley Qualls's Whateverlife.com attracts millions of them each month.

What's Free

So far, all the content: more than 2,600 social-networking page layouts that users cut and paste onto their MySpace and VampireFreaks profiles, as well as forums, advice columns, and Web-site-building tools.

What Pays

Advertising placed by Google (NASDAQ:GOOG) AdSense--Ashley's first source of revenue and still responsible for 60% of total revenue--and ValueClick (NASDAQ:VCLK) Media, a smaller ad network. Rates depend on traffic and page views. Google's cut is about 40%, Ashley says.

Nabbr splits revenue generated by its desktop widget, which plays music videos on the site. Ashley passes along to her fans CDs and signed photos of artists provided by Nabbr.

Businesses such as myYearbook.com have contacted Ashley directly to advertise on her site. With no intermediary to take a cut, it's far more lucrative.

What's Next

Pitching potential direct advertisers. Plus, cell-phone wallpaper downloads for 99 cents to $1.99 apiece scheduled to launch by September.