These aren't Mini Vans.
An arbitrary number like 20k miles has no meaning at all. Most RV engine problems are related to poor care of the cooling system. Buy one with documented maintenance, test all the fluids.
There are fewer of 2010's and newer due to the '08 crash. The Diesel Particulate Filter became required for emissions year 2007 and Diesel Exhaust Fluid for Year 2010. You will find nothing wrong with MH's built since '04/'05, although you may not have LED TV's or lights. The newer used ones, 2010 and newer, will be priced by the dealer as if they were really new. Without the benefit of the warranty period.
I've read that 5-7k per year is average usage. The reality is ISB's I would start to get concerned about 200k, ISC's 400K, ISM and above 600k and the same for equivalent CAT motors.
IMHO
