It a house. Is 13 years old? Forget the age and focus on condition. You've already found a few weak spots. Anything else? Batteries? Appliances? Water system? Generator running well?
Six tires are a major expense - big tires are pricey. The soft spot could be trivial or a big deal, depending on the extent of it and location (e.g. a joint vs elsewhere).
You didn't mention the size of this Access, but $33,000 is not a bargain, especially if it's not the biggest model (31 ft). In my opinion, damage and tires ought to mean a a lower price, maybe $27k. Less if its one of the smaller models. Don't be afraid to make a lower offer.