Well the thorp is close to an RV in speed, it really does depend on which RV model it is and what engine is in each plane. One thing to check is damage history usually in the form of a 337 but that is for factory built planes and am not sure if they are really required if the builder damages his own plane and fixes it himself. Damage history can be over rated as well because if a plane is put back together with new parts and is aligned well it is really as good as new (my 140 was a case of this) but the paperwork makes it seem like junk. Time since overhaul or SMOH (Since Major OverHaul) depends on the engine. Not all engines have the same time before overhaul (TBO) limits. Most TBO's are around 2000 hours though and most people that fly for fun will fly 100hrs per year or less. With a lycoming or continental engine between 100 and 200hp a major overhaul will cost anywhere from 10 to 20k. I would highly recommend getting something that flies somewhat regularly because like a car the more an engine sits the more things go wrong with it.