This topic comes up again and again. We can be most helpful if you conduct a thorough inspection, with comprehensive checklist in hand, so we can respond.
A pristine 2002 Classic 25', well maintained, with new tires, and new batteries, and everything working would be a nice find.
Check the following:
1. Air Conditioner
2. Refrigerator ( cools to 32-40 degrees in both modes)
3. Freezer (cools to 0 degrees in both modes)
4. Furnace ( lights and heats interior to thermostat setting and shuts off)
5. Water heater
6. Electric jack
7. Fresh water system (no leaks)
8. Water pump
9. Electric tongue jack
10. Trailer brakes
11. Tires (no more than 5 years old)
2. Floor covering
4. 12 volt
5. Window hardware
6. Any evidence of leaks
5. Spare tire
I generally start with a price in my head for that pristine Airstream that has been maintained with love and stored inside and subtract the value of each item that I must fix or replace.
I hope this helps.
P.S. I would love to find a 2002 Classic 25'