Subcontractors without Insurance

[Tom C]

I am hiring my brother inlaw and his crew to do a tear off and new roof on one of my rentals. In most cases, I wouldn't be too worried about it, but he is talking about using 7 guys. All of these guys do this work on the side. My concern here is that my brother inlaw nor his crew carries insurance and if one of these guys gets hurt on my property I could get hosed.

Is there a bullet proof release I can have these guys sign off on or is a release of liablity about as good as a hand shake?

Thanks