Many students find it cheaper to live off campus after freshman year. Those that remain on campus usually do it for the convenience of having finance and food taken care of, and of course, being closer to everything. There are on-campus apartments available for upperclassmen, and these are definitely an option to consider-the convenience of having a place to cook, more privacy, and so forth, without the hassle of bills and having to drive or walk to campus everyday. However, prices for these are comparable to the rest of RPI's housing; you can definitely live more cheaply elsewhere.
If the bottom dollar is the bottom line for you, then you should definitely move off campus. Even the nicer apartments are usually cheaper than campus housing. Some students choose Greek life as an alternative, and this is especially an option if you're a guy; all the sororities are on campus, but some fraternities are located farther away. Over forty percent of RPI upperclassmen live off campus, so if you're planning on having your own place, it's best to start looking early-cheap and convenient housing can be at a premium, especially just before the fall and spring semesters when it seems like everyone's looking.