Obviously the tyres will be shot, but my other concern would be that as it hasn't moved in seven years, it probably hasn't been serviced (or checked for damp). The upside to this is that as it hasn't been towed in this time, the body will not have been subjected to all the twisting/shocks that it gets while being towed, so HOPEFULLY the body seals shouldn't have become damaged. If you go for it I would get it serviced straight away (and fit new tyres before you go anywhere).