A terrific resource that not many incoming BUSL students know about until they get to Boston and pay a ridiculous "finders fee" is that BU owns several apartment buildings right in Kenmore Square, on Bay State Road. They rent these apartments to BU grad students and other BU affiliated people (visiting professors, etc. but not undergrads), and there is NO fee. And they only charge 1 month rent for a security deposit, and first month's rent. Most places in the Boston area charge first months rent, last month's rent, AND a broker's fee of one month's rent (I paid this my 1L year).
I got my apartment last August, right before I started my 2L year. I have a great 1 bedroom place in a brownstone, for $1250 per month (it was $1225 last year). I had no problem subletting it for the summer, for the full rent, and they're even letting me have a 9 month lease this year so I don't have to worry about subletting it for 2 months after I graduate and leave Boston.
They have studio apartments, 1 bedrooms, and 2 bedrooms. Most are located on Bay State Road, right behind the Citgo sign and the Barnes and Noble BU Bookstore, but they also have some in Brookline. They're hard to come by, but totally worth it if you can get one. I walk to school and can walk all over the city no problem. It's technically the start of Back Bay where I live. I don't have the phone # but they're located at 19 Deerfield Street (the street right next to the Barnes and Noble Bookstore) and they're the BU Office of Rental Property Management.