Great question,
especially for those of us thinking of making a few bucks with our tractors...
If you talk to your insurer, assuming you have a good relationship with a local agent, discuss exactly how you want to use the tractor. Discuss ideas like 'helping' your friend vs 'earning income' with the tractor.
I lost a tractor recently while in a town road. In my case the insurance issues and vehicle laws in VT were clear as I was on the town right away between two abutting parcels that I both own. Technically I was on my property which made for a much easier time of things.
The laws in each state and how the insurance companies operate are not the same. Do you have to have vehicle insurance to be on your roads at all? Do you risk loosing your license if involved in an accident without vehicle insurance on your tractor? Do you have any exception for farm equipment? Is that exception only for transport between two of your properties? etc etc..
Make a point of asking the questions now of your insurer and ask someone how knows the law at your motor vehicle department.
From first hand experience, it is a real bummer to loose sleep wondering how to pay off a new tractor while you wait for the insurance company to call you back. The one you called two days earlier to add the now totalled tractor to your policy....
Good luck...
PS: Some other potential gotchas for insurance.
If you were to roll your tractor by yourself and destroy it on your property, would your home owners insurance pay off? My bank had me look into that one before writing the loan.
Or, if it is on your trailer and going down the highway and something goes wrong. Do you have enough insurance coverage to replace the tractor that gets destroyed while being transported behind your trusty old favorite 15 year old pickup truck with legal minimums insurance?
Food for thought....