Sounds to me that you kinda answered your own question...
For what you are looking to do, in the timeframe you are looking at, it would be best to start with a gutted, but solid shell. You will save money & time in the long run. If you buy an "as found" trailer, then gut it, you may save money on the purchase price - but you won't know what you have bought until it's too late into the remodel. Then you will be at the liberty of someone else's timeframe and availability to get major issues addressed. If you start with a solid empty shell, it'll only be a "fit & finish" - not a potential total rebuild.
Vintage Airstream projects always take longer than expected...
Good luck in whatever you decide to do!
Shari