I've said it numerous times on this forum, but used/previous rental cars provide a potential huge value. The idea that you should not even consider purchasing one is ludicrous.
I purchased my 2011 V6 Premium Convertible in October 2011 with 24k miles on it. It was a former rental fleet car, was sold as CPO and included a Ford ESP warranty to 100k and was right at $20,000. This car had an original sticker price of $33,480. Other than the tick (which was fixed), an airbag sensor and a vert latch (both covered under warranty) I have had zero issues with the car. I do have a small clunk sometimes from the rear end that I'm trying to get resolved. The car looked almost brand new. The interior was spotless. There was one tiny door ding and a small scratch on the front bumper. I will trade that for $13,000 any day. We actually flew to Milwaukee from St. Louis to pick up the car and drive it home. Still saved money over a comparable local used car.
That being said, I would definitely have the car inspected or go through the Ford CPO process. If all checks out, no reason not to purchase it if it meets the value you need.
2011 V6 Convertible, Premium, Red Candy, White side stripes, Pony badges on fenders, auto headlights, lower fogs coming soon.