Tom, how many slides? It sounds like a cream puff with only 12,000 miles since it's a gas engine.
The normal things to check would be the batteries and tire date codes.
Was it parked for long periods with heavy usage on the inside?
More precise info would give us a better understanding of value.
Doing a search, I see there is one in Mesa, AZ, with just under 12,000 miles with two slides for $67,950 asking. It looks good and clean if that's the one. I see that an air conditioner has been replaced or the surround as the one in the back has a larger cover.
I also noticed that they have floor vents. If you have pets, you might want to keep those covered when not in use to keep pet hair out, etc.
Good luck,
MM.