The deal the saleswoman on the phone was offering seemed too good to be true: a 1,500-square-foot house in Phoenix, Arizona. The house, Suli told me, had four bedrooms and two bathrooms on one floor and sat on a 6,500-square-foot lot. And the price? $78,000 including broker's fees and renovation costs. It could be rented out for $800 to $900 a month, Suli said. That means even after the company's 8%...