Hello MC and welcome to the forums. Greetings from central Kentucky.
On buying the AS, set yourself a limit on what you're willing/able to spend, then go shopping. Do some comparison shopping on the airforums classified site. That's where we found Dora.
Prices will vary by size, age and desirability of the Airstream. Some are more collectable, so they will fetch a good price regardless of their condition, kind of like a '57 Chevy.
If you're thinking of doing the restoration yourself, you want to make sure to look at the mechanical things, like axles, no heavy frame rust and water damage that would require you to remove the shell. That is, unless you have the shop and skillset to do that kind of work.
There is a lot of information in here. Check out the restoration forum section for more information and advice.