Here is what I have found - the salt by itself is not the culprit, it's the gravel thrown up and under the car. It slowly chips away the undercoating and paint, then the salt eats the hell out it. If you trade your car every few years drive the thing 'til it drops. However, if this is a long term investment for you leave it inside during the salt months.

I have known a lot of guys who have had a neat car and drove it all year long (my son included). Then one day they wake up and decide to keep the car long term and were faced with a frame off restoration - those things are expensive.