Mobile RV service companies often offer this service. Some RV dealers/service centers. Camping World has a inspection service.
One thing to be aware of is alliances - if a service outfit also does service for the dealer you are buying from, you may not get a fully unbiased inspection.
Vince and Susan
2011 Tiffin Phaeton 40QTH (Cummins ISC/Freightliner)
Flat towing a modified 2005 Jeep (Rubicon Wrangler)
Previously a 2002 Fleetwood Pace Arrow 37A and a 1995 Safari Trek 2830.