Buying from a dealer that is no longer in the business is no better than buying from a private party. I look at water and cracks as red flags and I would find another camper without these problems. With water you have no way of knowing how extensive the damage and I would be particularly concerned about structural damage around a jack mount as this area takes stress when the camper is on the truck (tie-downs are in same area) and when the camper is off the truck.
If you want a camper for camping this summer buying a "fixer upper" is not a good move. Problems that can be corrected over time are one thing but this camper has a problem at the rear that I would want to fix before doing a road trip. It also could make the camper more difficult for you to sell later.
