That is a hard one, as it depends on your comfort level with RV systems. Worse case make sure they show you how to operate (and hence check for operational) each system in the coach. Heating, cooling, electrical power on ac and dc, water hot and cold, etc. Also take pictures as they show you where all electrical panels/breakers/fuses are located and also for the plumbing dump and fill access. Knowing where everything is will help you immensely if something decides to malfunction later on.