Laura Coe wasn’t planning on joining Airbnb as a host. She wasn’t exactly set on buying a house, either. She was interested and looking, but until recently, buying a home in Seattle’s white-hot housing market still seemed like a long ways off.

Then she heard about Loftium, a startup that ponies up the down payment for first-time buyers. And then everything snapped into place. With that financial support, she was able to put 5 percent down on a two-bedroom Craftsman home in a quiet alley in Seattl…