All the vendors we are looking say they are "licensed and insured".

Does that mean that if a worker falls out of my tree, that we are NOT liable for workers comp?

How do you check for things like that with a contractor.

Do you ask to see his certificate of insurance? Do you have to get him to write your house on the certificate?

If the contractor ends up bringing workers who are illegal (which always happens), and they get hurt, is the homeowner somehow responsible?