A friend's parents are going to stay with us for probably a year. They are legal residents in CA and both have their own health insurance. The only thing concerns me is the injury in the house. They are willing to sign on an agreement stating that they will not sue us for any injuries occurred to them in our house. Is this kind of agreement has any legal effect?

Also, they don't speak English. Can their son sign on their behalf? Thanks.

I suggest trying to get the agreement prepared in their native language if possible. If they are family members, they are probably covered under your homeowners insurance, so check with your home insurance carrier. But by signing an agreement, they may become tenants and that is a whole different set of rights, and they may need to have renters insurance to cover their liability, and you could be open to possible suit if the terms of the agreeement are not lived up to. I suggest that you consult a local attorney to discuss the differences and ramifications of the agreement. If you have this much fear, maybe you should not let them live with you for a year.