Margi Lee spent Memorial Day moving out of the historic farmhouse she'd lived in for the past year. After sinking tens of thousands of dollars into repairs on the rambling brick house, the 50-year-old college instructor in Boone, N.C., still was unable to get a mortgage on the place.

This is the worst-case scenario for rent-to-own real estate deals, in which a would-be homebuyer moves into a property as a renter, hoping his financial circumstances and/or the market will change enough in a year or two so that they can close the purchase.