Basiocally, everything should be working and the person should be able to turn everything on for you. 2008 is not that old so it should still be looking newish and clean.
At that age, there really shouldn't be anything burnt out or worn out yet.
My bigwarning signsI looked for on used trailers (mine were quite a bit older):
1.any obvious physical damage, seperated or "repaired" exterior seams
2. large calk spots on the roof, warping or staining of the ceiling and walls - indicates past leaks.
3. Soft spots on the floor
4. tire tread and sidewalls
5. Age/condition of the LP tanks and connections.check for leaks with soapy water. Completely empty tanks raises a red flag for me.
6. Check the undercarriage. If it is supposed to be sealed/enclosed then it should be. look for potential rodent holes
7. Look closely for any signs of damage to the hitch coupler
Mike and Kathy