When looking for my used motorhome, along with personal vehicles, I buy new from a dealer and used from the owner. My C now was from the original owner and I flew from Ca to Mn to pick it up.
Oftentimes a dealer purchases units from auctions. Having no history of maintenance you are throwing the dice. Many times they are re-possessed. if a person cannot afford the payment they surely could not afford regular maintenance.
Service records, i walk away if they are not available.
5 or 6 speed, most drivers could not tell the difference. My coach has 5,my truck 6 and my Jeep 8 . All deliver as expected.
Leaks and water intrusion. Overhead bunks leak, maybe not now but eventually. My Cambria has the sleek entertainment set up in the front.
When you find one, pay an experienced RV mechanic to look at it. A few dollars spent now can save you tons when you drive down the street.
Take your time, thousands of units out there. Travel if needed.
Self insure, extended warranties benefit the seller of the item, not the buyer. Ford V-10's are highly reliable and strong along with their transmissions. 300K miles is nothing to either one.
Enjoy your search and see you on the road......