Trailers that age are all about condition and how they have been maintained...really not about brand or manufacturer.
Leaks or past leaks are the biggie...Could be lots of hidden damage, mold, rot, etc. even if the leaks have been repaired.
Also check to make sure all appliances and systems are in working order...frig, water heater, electrical, plumbing, etc.
Both will probably need new tires. RV tires are about age - not if they still have tread and look good.
Good luck and offer less than they are asking.
"If we couldn't laugh we would all go insane."
Arctic Fox 25Y
GMC Duramax
Blue Ox SwayPro