All terrific comments toward finding the least problematic water problems in an Airstream . After purchasing 13 used A/S over the last 32 years, all living outdoors from Colorado to Southern Texas, here is what I learned. Age never seemed to matter. The oldest A/S I bought was a 1964
& everything in between including an Argosy & 3 A/S MHs. I had only one leak due to bringing an A/S from southern Texas to northern Colorado. The humidity change from Texas to arid / dry Colorado caused various seals to shrink therefore allowing water to enter the A/S. In another case, an A/S used on the West Coast beeches caused rust in various places often not seen until several years later when corosion appeared from behind such things as an A/S emblem.
My advise to find & avoid water leaks is look at the floor in a multitude of places beginning at the door. Then check the walls & put your nose to work for musty smells!