A few things to inspect on your trailer, very important!
1. Check for axle sag. There's a lot of articles out there on how to measure the angle of the arms and what not, but an easy check is that the rims are not up into the wheel well (looking from the side, you should see the whole rim, plus about 1" or more gap between the top of the rim and the wheel well trim
2. Make sure the dump valves work- take off the cap and check for leaking gray/black water
3. Stand on the rear bumper and jump on it. You should see less 1/4" or less movement between the bumper and body. This is an inspection for a common condition called "rear end separation" between the body and frame
4. Look down the side of the trailer from the back on both sides. The trim down towards the bottom should be straight. Another check for frame and rear-end separation issues
5. Check to see if there's a hot water heater bypass installed for easy winterizing
6. Hook up to AC power, and listen for AC-DC converter hum (the Univolt system it's called on AS)
7. Roll out all of the awnings if so equipped and check for proper rollup functioning and the fabric condition
8. Brakes- electric? Vacuum? Working?
9. Plug into tow vehicle (the towing connection) and check for turn signal and clearance lights working
10. Test operation of electric jack for hitch
11. Comes with load leveling bars? Important for the vehicle you describe
12. Check the skin for dents and check all seams to look for gaps and buckling
13. Check for signs of leaking tanks (fresh water, gray and black waste)
14. Test city water supply hookup
There's a few things to think about