From the pictures, it almost looks like someone tried to remove the clear shield and failed. It appears to be the same above the entry steps. As for the leaks, the one behind the drivers seat appears to be from the slide. Either it was not retracted fully when driven in the rain, or stored with the slide not fully retracted. The leak/stain in the slide area, I would be concerned with. As others have said, leaks are a concern, especially if they have been long term. The front outside is just cosmetic, but unless you can determine if the leakage is a one time thing, you may want to pass on this one, unless you can do major repairs yourself.
Wildmanbaker