In that price range, it is not the concern for a particular brand but the condition of the trailer overall. Start at the top and work your way down.
Check everything. Remember what seems like a small deal can be very expensive to repair/replace. A refrigerator will cost about $1,000 plus, new tires about $600, brakes about $600, a plumbing leak can be a simple fix, or unbelievably expensive depending on accessibility. An undetected water leak where wood framing has rotted can cost more than the trailer is worth to repair.
If you are not an experienced RVer, you would be very wise to first find someone who has the experience to properly inspect the RV for you, then find RV's that interest you.
As with any RV but especially with an older unit, you either need to be handy fixing things yourself or handy with your check book.