In that case, for $500, you probably wouldn't turn enough profit to make it worth your time. Offer what a junkyard would pay for the car, usually around here if you drop it off thats $300-$350 max. If it has mold under the carpets, it will take a long long time to get that out.

I would say buy it, Gut it, and make it a racecar. Drop in a built motor and trans and be done with it!