If the RV drives well and has good manners at speeds up to 65mph then all is good. Just like any used car. The majority of class Cs are on the Ford E350 or E450 chassis. If the Tioga has a V10 engine with 68k miles on it. That is good if it had the required oil changes and maintenance.
Look everywhere inside (including inside cabinets) for water stains and/or soft walls or floors.
I can only relate to my 28’ camper for sleeping. It has an RV queen in back and a standard queen (I think) in the cab over. So four friendly folks could sleep in it. I use the cab over for storage.
I will second the idea of looking at rental units.