Escape - rear wiper

This is not my car, but looking to buy this preowned 02 Escape, overall great condition, but rear wiper does not work. It sometimes rotates one time and that too real slow. What could be the problem and how much do you think it might cost for a fix? Thanks.

wiper motor most likely\W messed up. Depending on how the previous owner(s) was/were, they could have had a lot of snow on the windows and just used the wipers alone(front and rear) to clear the snow off.
Call the local Ford dealership and see how much they’d charge you to diagnose/replace it if it’s broken. Take that amount, and another $100 and deduct that from the asking price.

edit: Actually, if you have your own mechanic, take it to them BEFORE you buy the car and have them look it over front to back. They should find the problem with the wiper motor and anything else that might be wrong with it.