From our experience: Any rig you look at, require that all equipment is shown to be running. IE...have them turn the fridge on a day early (to make sure it gets COLD....not just showing it runs), have a battery installed to check out the lights, etc, run the furnace, run the A/C, have it hooked up to city water AND double check if the water pump works....by turning off the city water. Also have them start the water heater a day ahead......can you get hot water?? Have propane hooked up......does everything work on the range? Including the oven!
THEN.....after checking all that, and with water having been tested, NOW look for leaks.......:)
Why do I suggest this?? Because we didn't and ended up with a major problem with a spendy used motorhome. We've also had private sellers not have batteries, propane, or water handy.......and they try to tell you "everything works"...yeah, right...PROVE IT.
Good luck!