One peculiar feature in 1986 was the cabinet door construction. The inner panels were secured by a plastic extrusion (no longer available) which, over time, weakened and became brittle. It might have been designed to save construction cost and time during assembly. It's a pain, but very prudent to have them all redone.
Otherwise, look for the normal effects of age; plumbling leaks and seals. We bought ours in 1998, as a used 12 y/o, and over the course of sixteen years have replaced nearly every major component, i.e., water heater, refrigerator, microwave, A/C, drapes. In return, we've trailered it > 40K miles, lived in it for 7 AZ winters, and frequently use it as a studio apt/guest room.
A foremost expert is Forrest McClure, a regular columnist and blogger for the Airstream Life magazine. He can be accessed through the magazine's "community" site.
South Bend, In
DeTour Village, Mi