Hi, and welcome to the forum!
Airstreams as a rule do not need much in the way of "caulking"
The main reason it seems to be discussed here is we are forever replacing stuff the is skin penatrating, like new roof vents. ther is some cauling that may need to be maintained at the tops of the trim strips taht run around the trailer, but is there is none now don't worry about it. Most of the older trailers have had owners that had a leak at some point and instead of taking the time to find it and fix it they got out the caulking gun and the silicone and messed up a perfectly good trailer. There are others that wer caulked for no other reason than "I don't want it to leak" not there ever was one. It sounds like your current owner knows his stuff.
I don't know what kind of deal you got, but if the rig is clean, has been maintained, and is the size you want, you done good. Good ones go fast, so don't delay!
WBCCI #5501 AIR # 49
1978 Argosy 28 foot Motorhome
Wise men talk because they have something to say; fools, because they have to say something. -- Plato