Welcome, Whiggs. Check the Classifieds here for some comps. The four pictures you posted look nice, but there is a LOT more that needs checking. You might want to make use of one of the inspectors here. You might also try contacting the local Unit to see if anyone there actually knows the coach.
Since you mention that you have neither the time nor the skill to renovation I'm wondering about your comfort level when it comes to maintenance. You are looking at a coach that is more than 40 years old. They are going to be issues that come up. Are you up to that? If not, you will need a healthy credit card.
I speak from experience. We have a 1993 Foretravel. We drove 150 miles yesterday without incident. This morning we were ready to go, and discovered that there was no coolant in the tank (full yesterday noon) and a wet spot on the ground. Two hours after the first call the tow truck arrived. Another hour or so and they had the coach hooked up and ready to go. Two hours after that we arrived at a truck repair shop. We're now in a hotel room and the coach may be ready sometime tomorrow. Cost will probably be a coach buck (1 coach buck = $1000).
An Airstream may not have anything that expensive, but you aren't going to get things fixed by the local shade tree mechanic. If you can't fix it yourself you are going to have to pay someone else, and that may well cost you well over $100/hour.
My suggestion would be to check the Classifieds for a similar-size coach from the late 90's or early 00's. I suspect that you can get one of those for your $15,000 and have fewer headaches. Just my opinion.
David Lininger, kb0zke
Heartland mpg 181 (sold)
1993 Foretravel U300 (for sale)