Refrigerator is number one. Make sure it runs on propane. Take no ones word. Ask them to have it running long before you get there. I'm not sure how you will know at this time of year in your neck of the woods but at least make sure the burner on the back of the fridge lights. Water pipes would be next but it has probably been drained of all water for winterizing. You don't want a water leak. That can be real expensive due to the pipes running behind cabinets. Propane furnace should be easy to check. Roof air will be tough this time of year. Generator should run smoothly and run microwave and roof air. Many times if they are not exercised regularly the carburetor will gum up and at that point is pretty much dust and will need replacement. I changed mine myself for about $200 plus my own labor. You've got a mechanic to check the drivetrain so that should be good but as you know things will happen. Tires should be no older than five years and should be LT truck tires not P paasenger tires.