Even though the University provides housing facilities for all undergraduate students, and even though all freshmen are guaranteed housing, the higher your classification, the less likely it is that you are guaranteed a spot in the dorms. Because of this, most students start looking around for apartments and house-shares close to campus as early as sophomore year. There are a lot of convenient off-campus options in the city and in the suburbs of Maryland and Virginia that are within the metro area, and sometimes these options are cheaper than the dorms. Some of the more popular locations are in the Shaw district within walking distance of the main campus. And while the landlords of these apartments or houses usually rent out for prices that students can afford relative to living in the dorms, one of the cons of living in some of these locations is the fact that students are more vulnerable to the dangers of city living. Just remember that you won't have the benefit of having the campus police around.
Some of the best areas to live are actually outside of DC, and while the commute can be as long as 45 minutes to an hour, the added sense of security that comes from living in the suburbs is worth it. The prices in these spots are often very low; the farther away from DC you go, the more inexpensive the prices for apartments and house-shares are. And you can always count on the Metro to take you into the city.