Instead of hiring an "RV inspector", consider hiring a mobile RV repair man. Get references, call and explain your situation, i.e. you're looking at used RV's and need someone who is well experienced with RV chassis ( engine, transmission, brakes, heater, dash AC, windshield wipers, suspension, and exterior lights) as well as the "housebox" (i.e., exterior paint and graphics, roof sealing, RV generator, house battery and converter charger, roof AC, awning, fresh water pump, toilet and holding tanks, water heater, fridge, microwave, propane system and detecting water damage.) Explain that you will want him to check operation of all items, and give a detailed estimate, parts and labor, of what repairs, replacements and upgrades will be needed. I would expect that type of testing/inspection to take up to two hours and cost you some $200 or more, but it could help you avoid buying a "money pit" that could ultimately cost you much more than it's market value.
If you have have read all these recommendations, you are already better prepared than we were when we bought or first used Class C "moneypit"