Hello twall7 -- Welcome to the Forums!
Finding a used Airstream can take some months of cruising the classifieds here and at the Vintage Airstream Club
site. eBay has the occasional good Airstream find but often is the last resort for selling worn out units (ie, needing major rehab) -- I'd avoid it unless you were able to inspect before purchase and know what to look for.
There is a wide range of potential issues and more complications as units get older. Rehabbing a true vintage (>25 years old) gets very involved (2-3 years in many hobbyists hands). Models from the late '80s through the 1990s are more ready-to-use -- but never be surprised if they need a significant investment (eg, new tires, fridge replaced ... so many things). Shorter Airstreams are in high demand. Longer Airstreams from the '70s into the '80s had weak frames and were subject to rear end separation (search on those last 3 words).
There's no secret -- it just takes steady work to find your Airstream. They've gotten a lot of publicity in the last year and good ones too often are sold the day before you'll call... Work hard but work quick when you spy a prospect. Best wishes!