Each situation is different when you buy used so there are a lot of things to consider.
First, are you buying from a private seller or a dealer. It makes a difference.
If buying from private seller, are they upside down on the coach or do they have equity in it? Are they under duress or just getting out of RVing or moving on to another unit? How have they maintained the unit the way it was supposed to be maintained? Does everything work?
If you're buying from a dealer, did they trade for it or buy it at auction? How much do they have in the unit? Do they have to put any money into it to make it sellable? How long has it been on the lot.
Buyers have to do a lot of research and expect to pay for things like inspections to make sure you are getting a good deal on a good coach. We paid for an inspection, then walked on the deal when things were found that we weren't comfortable with.