I'm not a lawyer, especially a lawyer of a foreign country, but I don't think a guest (because that's what he is) would have any such rights. However, if he has officially changed his address to Sapphi's place, then it might become a problem like that, although even in that case Sapphi could probably deny knowing of it. And like you said, the NYU likely would or could not even allow it officially, rendering the whole nonexistent contract null.
It would indeed have been better if the fool had decided to either wash or leave peacefully. Anything beyond is unnecessary drama that someone who allowed him to crash for a while does not deserve. This equals to biting the hand that feeds you.