Pay special attention to the cab over section. Look for any buckling where it meets the main box, they tend to sag.
Start the generator and run the a/c
Look at the back of the fridge while running and check for any yellow residue.
Close the doors while inside and SMELL it. You can tell a lot about a camper by the smell. Pets, smokers, musty, dirty, waste tanks, oil, burnt, etc are all things "The Nose knows" ;)
Take it for a drive on the highway at 55mph. Check for any pulling, wobbling, or noises. Take it very slow over a few bumps and listen for any hard thumps.
Drive up a steep grade and see how it pulls. If it seems like it is really heavy, that's one thing, but if you basically have to floor it and it still crawls, it could be a sign of a worn transmission.
Check the date code and condition of the tires. They can be quite pricey.
Look at the batteries. Look for corrosion, swelling, date of installation. See if the wiring to the house battery looks corroded or any signs of melted or damaged insulation.
Check oil level and if there is any burnt smell to it. Check coolant level. Do same for transmission.
Take a look at the underside for excessive rust, especially brake, gas, transmission cooler, etc hard lines. At 12 yes old, these could be a major pending problem or none at all.
Put the awning out and open all the storage compartments. Look for signs of rust or bad smells.
You'd be surprised how many awnings have rubbed trees when backing in or pulling out. Long body and top tilts, both the driver can't see and boogers them up.
Look at the trim of the windows to see if the sealant looks OK or is showing signs of cracking, moldy looking, etc.
Hope thismhelps. :)
