I would look at those built in late 2005 and above. The designs of the slides and interior changed. For any TC with slide, look at the area of the walls near the slide and in each outside compartment. Damage can be caused by putting too much weight or other hard wear on either.
Otherwise, standard checks apply to look for water damage, appliances working, etc.
I have a 2006 double slide, and it has been fine with the exception of a failed Dometic AC. Not specific to a Host, but a failure nevertheless that is due to vibration and the tubing breaking.
If the TC has been stored outside, the awnings likely need replacement and the decals are probably about gone.