Buying A Rental Car?

Should I buy a used rental car directly from Hertz/Avis etc?

So one of my coworkers has been buying cars directly from Hertz with their rent to buy program. He hasn't had any problems with the 3 Toyota's he bought from them. I think you rent the car for a few days, and if you like the car you buy it. If you don't, you pay the rental fee. This gives the buyer an opportunity to take it to a mechanic and have them check out the car.

So, what do you think about this? Stay away? Or go for it?

Thanks. Patrick.