Maybe property damage isn't the biggest worry. Hurting someone is. Someone that may not sue you for property damage (as in a friend) often has no choice whether to sue you for injury. And, that is usually millions.
Many years ago, our bush hog mower threw a baseball size stone, through our house window a couple hundred feet away. An opposing panelled wall in the house got imbedded with the glass. Good thing, no one was in the room. ACCIDENTS DO HAPPEN.
And the other thing is, it does not seem to matter who is to blame. It's where the money can be had. I heard of how the law works in Ontario. If two people are in a partnership, and one has money and the other doesn't, and the poor guy makes a mistake, that you get sued for, the blame goes to the guy with the money.
In other words. If you don't have a pot to piss in and no insurance, you are in the best possible position to do contract work. No lawyers will have any interest in you at all. ****, they will probably try and sue the maker of your tractor.