I would call the law first, but as sure as the sun rises in the East if that man had drugs in that house, around my babies, he would leave, either willingly, or feet first. it doesn't matter where he gets his mail, if he is asked to leave then he should be made to leave. If her dad is aware of it, as their landlord, he has the right to have him removed from the property because of the drugs. If its meth, the EPA or whoever can come in and condemn the property, so its in his best interest to take care of this problem as fast as he can. This is not a rare occurance; it is so sad our country has become the mess it has become. I hope the best for your family member; I know this can't be easy for her!!!