Welcome from the Florida Panhandle
Welcome to the Forums. We're glad to have you with us.
The guest cottage thing sounds like a really neat idea. A Vintage Airstream would be the way to go. You're in luck wanting a larger trailer. When it comes to vintage, the bigger the trailer, the smaller the price. You may even find a great price on a unit with bad axles. You could have it flat bedded to your lot, and since it won't be going on the road, the wheels are just for looks.
Good luck in your search. If we can help, let us know
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)