I don't know what sort of insurance he would get that would protect you from liability, unless he is going to have others on the job with him who might get hurt. If you are worried that the carpenter will get hurt and make a claim against you, then I think you would be looking to your own insurance for protection. As a major caveat, I have no idea how things are done in New Jersey, so treat these as food for thought.

You might want to run all of this by your insurance agent.