OP ..... as mentioned by others, it's no different from the owner/landlord having a key, usually a master key that can open every room.
It's common practice ..... what if there's an electrical fault in your room and a fire breaks out and your not home, he needs access, or a water pipe bursts ... he needs access.
It's no big deal, just hide valuables or lock them in a bag, also put a camera on the door if your that concerned.