If its in as good a condition as you describe, it could easily be worth the price if the vintage appeal works for you and you really like the trailer. That's the biggest factor if it's in as good condition as described, do you love it enough.
If it's been cared for enough to keep it in such good condition then chances are you'll probably have few issues. Make sure the fridge, ac, and as many systems work as you possibly can. Try to get electric and water hooked up so you can test out all the electrical and plumbing.
I'm sure there will be things you'll want to upgrade, batteries, converter, tires possibly depending on what's there.
25' is a good length too, long enough to be comfortable in but not so long to be difficult towing or getting into most campgrounds.
If you don't buy it I might!