Welcome to the Forums. You'll find a lot of really good info here.
Spend some time and effort shopping and researching Airstreams. Check all prices including new. This will give you a true value basis.
Avoid units that need a lot of work unless you want to bring back a rare historical piece. Parts are expensive and so is labor on portions that you can't do yourself. Sometimes a unit that needs a lot of work will end up costing substantially more than a good, solid newer unit, and that doesn't even include your time.
Shop Airstreams everywhere. If you call on a unit and it has already sold, ask the buyer if he will tell you what it went for. Knowledge is power.
SuEllyn & Brian McCabe
WBCCI #3628 -- AIR #14872 -- TAC #FL-7
2015 FC 25' FB (Lucy) with HAHA
2005 Suburban 2500 Quadrasteer (Olivia) & 2011 Silverado 3500 (Fred) with Outfitter Truck Camper (Ethel)