Thor is the largest rv mfg. And they're the worst IMHO. We've owned more than one of their product platforms. They buy up their competition ( that were good on their own) and the quality takes a dive. Never again will we own a Thor made product. They make them look really great, but that's where it ends for them.
As far as buying a rental. I personally never would consider it as most people renting these things could care less what they did to it or how they drove it, much less knowing anything about them.
If you looking for used, I'd buy from the original owner. Not a dealer. Preferably someone who has all the service data. Even ask if they warranty for problems for 6 months ( in writing ). You never know when someone is trying to get rid of a lemon at your expense.
Many people trading a MH in at around the 5 year mark are doing so to get into a newer model. But it could be at the point tires and batteries are at the replacement point. The cost to do that could be around $5000 or more. So they use that cash as part of the downpayment on the new, or pocket it . You might be laying out that money they saved after your purchase. If you get a really good deal, that might not matter, but it should be part of your negotiation with the dealer or private owner.