One of the reasons we moved the conference to June (from May) is to provide affordable housing on campus. If you prefer to stay outside, budget is $350-$450 per night.
The campus housing hotel is exceptionally good in quality. Here is the link for 10 Buick Street accommodations for PMiP registered guests: http://stay.bu.edu/PMiP.bnb
Beautiful apartments and scenic views of the Charles River. Yes, they will sell out.