Hey Canadian Bob,
My Airstream, a 1986 tradewind, sat for two years prior to me buying it.
1) The previous owner was a great guy and filled me in on all that needed to be done.
2) I found that the house battery, although little used, needed replacement to bring it up to voltage specs.
3) My tires/shocks and wheel bearing re-packing had been done by the previous (PO) and were in good shape.
4) I had to "bug bomb" my trailer, twice, to get ride of bugs that had made themselves home.
5) My new fresh water tank installed by the PO had a bad taste / smell. I emptyed the tank and started a rehab program.
I added 1/2 cup of clorox to 5 gallons of freah water, then dumping the mixture into the freah water tank. I then filled up the tank with 30 gallons of fresh water and let it sit for 30 minutes. Then I pumped out all the fresh water.
I then added half a box of baking soda into 5 gallons and dumped that mixture into the freah water tank. I then filled the freah water tank full of freah water. Let it set for 30 minutes.
Pump the tank out, then refill with fresh water. The water should taste great.