Maximum a grand and that is if everything works. If the fridge is iffy, thats a big expense and old fridges suffer from congestive cooling failure a lot.
Pretty easy to ascertain just how much water damage there is without disturbing anything, just look under the mattress in the front for staining, inside the cabinets at floor level, staining and at the floor itself for obvious bubbles which are indicative of water damage.
Campers with conventional front windows in the cab over are all suspect.