We bought one from a dealer who specialized in repos. It was dirty and we had to make some repairs and buy a new water heater, but that was about 3 years ago and its still in great shape. I think we spent $5000 for it and put in less than another 1000.
I think if your willing to do the repairs, consider that they usually have been poorly maintained and will need to have every appliance etc, rebuilt or replaced or at least maintained. Will need new tires and probably a new mattress, and lots and lots of elbow grease.