You guys are a few years a head of us. I retire in about 5 years and will be looking to spend from 50 to 80k. My general thought is get an RV that someone spent 200 to 300k on 10 years ago. After looking at the Itasca I saw for sale (online)I would have to at least look at them.
I do know about the onan 4k generators. If buying from a private owner I would take my Kill-a-watt meter (20 bucks at harbor freight) and check for a good voltage/frequency with the AC running. Might give you a little more wiggle room if it's not working correctly.
Good luck with your purchase.