Really depends on where you are vs how much damage. Heavy dew areas with salt spray you're going to pay the price. In high salt areas 2-5 miles inland seems to be a good distance for short term RV'ing. 50 miles inland and the damage will not be noticed.
Fresh water rinsing is needed. Ospro when you see rust. Swap out all screws for SS ones before you can't remove the old ones due to rust. Rinse off the aluminum fins on the AC unit with fresh water so they don't rot. Grease the fan shaft on the AC unit before the shaft rust thru. Spray the underside frame with oil (I use ATF) or check out Fluid Film for more $$$. Make sure you hit the leaf hangers. Oil anything that is steel and is exposed. Then sit back with a beer and watch rust slowly appear.
Good Luck.