This isn't, technically, a refi, but it's close. Mortgage-free homeowners sometimes get mortgages to put cash in their pockets.

"There's a lot of people who don't have a mortgage," Hackett says. "Maybe they want to go to Florida, buy a second home with cash. So they cash out their first home and take the cash and go down there and don't need a financing contingency, and they're in a better position to bargain."

They could also take out a mortgage on a paid-off property to start a business or for other reasons.