Make sure you personally inspect the roof and look over the entire rig very carefully for any sign of leaks. If it hasn't been maintained properly and you find evidence of even small leaks that could be a sign of hidden water damage. Not to mention that the previous owner didn't take care of it. Get a flashlight and look under all the cabinets, especially at the front and back where the end cap seals can fail. Also look carefully around the skylight if it has one as this is a common area for leakage.
If you do find evidence of water intrusion, but you are just in love with this rig and think you can live with it, use that information as a point of leverage with the seller. At least make them replace or re-seal the roof or no deal.
2010 Flagstaff 829RGSS
Still to go: AK, NL, NT, NU, YT