Comment by pjdemers

In the US, there is title insurance. If the seller didn't have the legal right to sell the house, the house reverts to the legal owner, and the buyer is paid back by the insurance. It's not possible to get a mortgage without title insurance, and a cash buyer would be nuts to not demand it from the seller. In some states (example, California) it can get more complicated, though, because the right to sell a house isn't the same thing as the right to live in it. They buyer may own the house, but not have the right to force the current occupants to leave. That's why it's important to state in the contract that the house must be completely empty before the seller gets paid, and every month that it is not completely empty, a few thousand dollars is subtracted from the purchase price.