Like the other member are saying look at the roof , when you go look at one ask the owner to set it up fully extended and ask him to put it all down and fold it completely down , while it is up if it has a A/C turn it on make sure it works have him fill the fresh water tank make sure your water works and also , if it has a cassete toilet have as if you can flush it , make sure the enters door is all complete and sets in properly , all these items are very expensive so you want to make sure what you buy works , or at least you know what does not work properly , Good luck