Did you guys check with admissions about housing? They sent out an email to the May class asking for anyone who needs help with housing to contact them. They are trying to connect people. Online, I would look at Craigs List-- it's not great for outright rentals but is very good for sublets and such. You should definately be able to find something because lots of people vacate the city during the summer.
I've lived in and around NY for a long time, so PM me if you have specific questions about neighborhoods, trains etc.