Reese and Kyle Rademacher weren't sure how they would afford a down payment to buy a home until their real-estate agent mentioned an offbeat idea: crowdfund the money from friends and family.

Mrs. Rademacher, a 28-year-old construction technician, set up an online profile with a program called HomeFundMe to solicit donations. Her parents and a few others responded, and in March the Rademachers closed on a $320,000 home in Cheyenne, Wyo.