Airstream Guesthouse

Something we have wanted to do for a while now is put an Airstream in the backyard and use it as a guesthouse.  I have all sorts of ideas and visions (as usual).  It is really just the logistics at this point.  Money, obviously, but also, would anyone want to stay in it?  Do we buy an old one that maybe is not fit for travel and just leave it there, or do we get one we can tow so we can take it to the farm and "camp" our way across the country?  I routinely check them out on craigslist, but there is so much I don't know about travel trailers.  What to look for, how to spot problems, what part of the airstream is the "tongue."  

I've been looking for a picture to do my vision some sort of justice, but there is none to be found...