I would consider 12k miles to be a red flag. RVs that just sit for a long time can have problems. Seals dry up. Bearings aren't happy. Etc.
But, I would imagine that you're getting it at a good price. Check everything out very thoroughly. Drive it for a hundred miles or so. Test everything.
Good luck!
2008 Georgetown DS350 Class A
Wife, kids, dog and cat