I assume you have driven it? Does it handle okay? Does it pull to either side under way, or have any vibration in the steering wheel or shimmy action in the front end? Does the engine start easily and run smoothly without smoking? Assuming it has typical mileage for a rig of its age, the suspension deserves close scrutiny, especially the front end. Have it checked for alignment, condition of tie rods and tie rod ends, and condition of the king pins, and have it checked by someone who regularly works on motorhomes. If king pins are not kept properly lubed they will wear rapidly and can cause significant problems, and they are not cheap to replace. New king pins for my 38' Monaco cost nearly $2,000. Also check the shocks. If they are the original shocks they are no doubt in need of replacement and good shocks for a sizable coach will cost around $125 to $200 each, depending on brand and quality, plus installation labor. I assume you have tried all of the appliances; fridge, water heater, water pump, furnace, TVs, TV antenna/satellite dish/receiver, etc? If you haven't, do. Make sure they all work and not just for a couple of minutes, but for enough time that you are sure they are okay. Tires are another big dollar item on large coaches, costing in the neighborhood of $400 to $600 each, plus installation costs.
If you are not familiar with large coaches have it checked out by someone who is, and someone who is not associated with the seller.
2007 Itasca Ellipse 40TD "High Plains Drifter"
'02 Wrangler Tender