I like many others have stated would let him pay full cost for the repair. If I were operating my equipment anywhere then I would feel responsible. If someone else tears it up then they should cover it. Two years ago this December I bought a brand new 700cc four-wheeler. Top speed somewhere around 75 mph. Had a friend come over one night to look at a deer I had killed. He kept looking at the four-wheeler and I offered for him to ride it if he wanted to. At that time the bike had 9 hours on it. Keep in mind this guy teaches four-wheeler saftey courses. Without much thought he jumps on it, pins the throttle and across the field he goes. This was about an hour after sunset. As I am watching him leave he gets a couple hundred yards away and hits a hole, grabs the front brakes and goes end over end. By the time I got to him he was unconscious and blood trickling from his mouth. I thought he was dying! In the end he had a slight concussion and several broke ribs. The four-wheeler wound up with a bent frame and several other damaged parts. I looked around for the best repair job and price. I found a guy that worked at the local dealership that also did work at home. I got him to make repairs and the guy that wrecked it offered and paid the total bill. We are still friends today. I felt bad at first for the situation he was having to deal with, but at the same time didn't feel I had done anything to have to fork out over $2500 in repairs on a brand new machine. More recently had a starter to go out on a friend's Bobcat machine. He leaves it under our barn and allows us to use it as it is ours. Since we were using when it quit we picked up the bill for it. In my eyes that is just a risk you take if you borrow someone else's stuff. Apparently the friend borrowing your tractor feels the same.