The stain by the AC wouldn't worry me. As others mentioned, check the wall and floor around the window that leaked for soft spots. If no soft spots, then I don't see a problem.
I agree to have them turn on the fridge before you arrive so you know it works on electric or propane - you can always fix it if one or the other doesn't work, but if both don't work you will need to replace more than likely.
If those check out, and either you or a mechanic check the engine, etc., then it's just a matter of floorplan and price. Is the floorplan really what you want and is the price acceptable. If either answer is no, then keep looking.