As others recommended, Walk through 1st.
The good news is since the trailer you want to purchase is a 2008, most of the new TT issues were already taken care of... missing trim, badly aligned cabinetry/doors, heater/AC vents, axle alignment, water leaks caused by poor workmanship...
The bad news, you need to look closer at yearly maintenance items, all appliances working, slide-out in/out no less than 10 times and specifically, everything related to if there are leaks from 8 years of use and travel. Hopefully the TT is fully closed when you arrive and check for the initial smell... musty, damp is potentially very bad. Look at all interior walls and floors, behind couches and check for soft spots, damp carpet, etc. Check around windows and beneath windows for signs of leakage. Then, somehow you need to inspect the roof... most critical. Look to see if it appears regular re-caulking of seams was done. This may be more difficult to determine by someone with limited experience, see if you can bring along an acquaintance that has knowledge. Check around all external lighting and see if the trailer side looks wavy/warped <-- sign of a leak or previous leak. I would also inspect under the TT and look at the frame for any signs of cracking/stress. Topical rust will probably be there and wouldn't be much a concern unless the rust was really bad. Test all propane appliances, heater, fridge, stove top, oven, propane detector, smoke alarms. Then connect shore power and check everything again that uses 120v AC. Connect water and check water heater and all faucets/toilet and check for water pipe leaks.