Off-campus housing at Yale is easily available and close to campus. However, most students choose to stay on campus for all four years. This is due primarily to the residential college system that groups room, food, friends, support, and activities under one roof. Yalies are required to live on-campus until their junior year, and by the time the opportunity comes to live off-campus, they are usually too fond of their college situation to want to leave their friends and social groups. The decision to move off-campus means a certain amount of separation from the Yale community; food, Internet, and safety become your responsibility instead of your college's.
That being said, those who choose to move off-campus are usually very happy with their decision. Off-campus living offers more privacy, independence, and a break from the Yale campus. If you're frugal, off-campus living can help save on expensive dining hall plans. Living off-campus is also helpful for students who may spend a great deal of time in one area far from their residential college, like Science Hill or some athletic facilities. Some students choose to rent a house and split rent between 6–12 friends. Others prefer their own single-bedroom apartment. It's really all about how you study and live best.