Door locks....emergency help please?

I will be moving into a shared house with other students soon. As I am slightly worried about my personal property, I wondered if there was any chance of getting a lock for the outside of my bedroom door? I really don't mind people coming in there when I'm there myself, but I don't like the idea the idea of leaving all my worldly goods open to everyone in the house when I'm not there. If anyone knows of any simple lock I could fit on the outside of my bedroom door for me to lock when I leave please let me know. The cheaper the price the better also!! Thanks.