Think the 986 can be a real good dirt car. Mid engine, RWD.
50 bucks a day sounds really good.
And be careful: too much paint means too much weight.
I think it could be interesting to get more cleareance to the ground. So maybe with different, higher profile tyres or a kind of a lift kit.
Maybe you can get old Cayenne or Touareg rims and tyres / wheels with all terrain tyres. They have 5x130.
So you can get something like that:
Regards, Markus