Freshmen are required to live on campus in Harborview Hall, and almost everyone else lives at Wagner, unless they commute from their family’s home in the immediate area. Wagner doesn't contract out housing for undergraduates, which may be why only a very small portion of the student body lives off campus in the traditional sense (not with their parents). The rents around Staten Island can be pretty reasonable, especially if you can find a couple of roommates, but the room and board fee at Wagner includes utilities and food, so it is still cheaper to live on campus.
If you really don't want to live on campus and you can afford food, gas, and car insurance, it's pretty easy to find an apartment. A quick Google search will get you tons of hits. It’s suggested that you drive by the areas in question just to make sure they’re not too far from campus or in really sketchy areas, but honestly, since you're a college student, you'll probably have to live in a sketchy area sometime in the future, and there's no time like the present!