There was a good thread about this awhile back.
I live close to the Indiana hub of RV makers and coach builders. So I see a LOT of them either being towed or driven to dealerships.
One forum member noticed salt damage on his undercarriage although he never had it on the road during winter nor lived where it snowed.
THIS is IMHO the key factor on WHEN you order your RV.
Our roads are HEAVILY salted during the winter months. And the salt stays and when spring rains come you still have salt all over your vehicle from the road.
If you order your RV or look when it was made. If it was made during the winter months your RV WAS driven on the interstates loaded with salt.
AND once at the dealership they might get a quick hose down on the outside if it's a lot, but they are NOT thoroughly washed on the undercarriage. Thereby sitting on the dealership lots sometimes for months on end with salt encrusted undercarriages. Just saying something to think about.