If he wants to try to find housing himself, he can try Craigslist for Western Mass.:
http://westernmass.craigslist.org/
Most university web sites are completely useless (i know mine's is) so a call into U Mass's international students office might get more results.
He might also do well to call the secretary (or admin. assistant) of the department he's joining. They are the ones who know all the ins & outs, and probably have some good insights into housing; she will also probably know who else is joining the department in the fall and might be able to connect your son to potential roommates. Plus all American women are complete pushovers for British accents (this part of "Love, Actually" is true; it can be the only thing to account for Hugh Grant's otherwise inexplicable success over here). So an actual phone call couldn't hurt in terms of getting some results.
When I went to UCLA in the 80s for my doctoral program, the admin assistant was able to make a phone call and get us into married student housing, something that the school's literature never bothered to mention was even possible.