SEATTLE, Wash. -- Laura Coe never expected to buy a house before she was 30.

The 29-year-old Microsoft finance manager has been renting in Seattle since she moved here in 2010, and remaining near the city’s urban core is important to her. With Seattle’s skyrocketing home prices, she thought it would take years of penny-pinching before she could afford a home in a neighborhood where she wanted live.

Then she heard about Loftium, a new startup that helps homebuyers with their down payments on the condition that they rent out a portion of their home on Airbnb and share some of the profits with the company.

Loftium officially launches in Seattle today. The startup has been flying below the radar while awaiting regulatory approval but Coe got the inside scoop from a friend who works there. With Loftium’s down payment assistance, today she is closing on a two-bedroom, two-bathroom craftsman home in Capitol Hill.