Nadaguides list that unit at $9600 average so your not too far off. It should weigh about 5000 lbs GVW is a bit over 6k. Look up your TV's specs and make sure they can handle it.
Take a digital camera with you and take pictures of any questionable areas. Then you can post them here and we can tell you if you should be concerned.
Things you need to look for:
Inspect the roof for tears and caulking cracks that would indicate leaking. Minor hairline cracks in the caulking are usually not an issue but need to be taken care of right away.
Inspect the exterior sides for signs of bubbling indicating delamination.
Operate every electrical item you can. (slide, water pump, lights, fans, etc)
Operate every propane item you can (stove, fridge, furnace and water heater).
Check tires for uneven wear and air pressure.
Hook it to the TV if possible and make sure the lights and brakes work.
These and just a good general overall inspection should give you an idea what shape the unit is in.
You can search this site for Ky-Dan's posts that has a PDI (predelivery inspection) list and use that as a go-by. This is not a new unit but a lot of the items still apply.
Salem 29RKSS Pushing a GMC Sierra 2500HD!
Gotta go campin!