Spend at least 45 minutes on the roof checking all the sealant inch by inch, if you see any suspect spots, then check the ceiling in that location extra carefully for signs of water intrusion, sames goes for tops of doors windows, and slide outs. If you find signs of water damage run away as it is likely far more extensive, and far more costly to repair than you might think at first. Continue down from the roof on the outside, checking all other sealant seams, compartments, etc. then check the under carriage. Once you are done with the body structure, move on to appliances and other systems, expect this process to take 4-5 hours to go over everything.