My question involves landlord-tenant law in the State of: New York
I am the tenant of record in the upstairs apartment of a private house. My housemate, who was my tenant and not on the lease, got the last of her stuff out today (July 9, 2017) (she has been staying in her new place for several days) and returned one of two sets of keys. I asked her to leave, giving her 30 days written notice after she ignored 60 days verbal notice. She still owes me 1/2 of her June rent. We agreed that she could stay the week + of July rent free. The keys I received from the landlord and shared with her on moving in were 1 mailbox key, two building door keys and 1 apartment key. There is a 2nd apartment door key which I have never had. That's the background. My question is, may I (with my landlord's permission) change the lock on that second apartment door lock (giving the landlord a copy) before she returns the second set of keys or pays the last agreed upon rent?

