if you go for one get the older version , the 2 wheel drive ones will go anywhere.
it's like every thing with a engine!!! look after it and fix it right then it;s there to enjoy.
there is so much you can do to them to improve the running etc. early ones are 6 volt
so that's the first change to 12 volt. etc there is a good forum for them as well.
i will try and find it.......