I entered into a roommate situation with a friend, as a sublease of her mother, who is the only person on the original lease. I signed a "promissory note" to the mother. Since moving in together, the friend and her mother have told me who I can and cannot have at the house (namely my boyfriend's children), yet the roommate invites whomever she wants over and her boyfriend is now living there, rent free. After the last episode of the roommate being hostile to me when the kids had an emergency and had to come to my house, I decided to move out. I am paid up on rent for this month and the mother still has my security deposit, which will more than cover any exiting bills. She is threatening legal action against me. What can I do?