Also I lived in Boston for the past ten year, by Northeastern and then in Somerville, and commuted to BU via the T. Red line to green line took about an hour tops, but it really was never a problem (although I'm glad I'm not living there this year with all that snow)!
If youre close to a college, rent can be outrageous. A one-bedroom can easily go for 1500-2000 a month. It's absurd. Looking farther out like the others have said is a good bet. I was really lucky to find a place in Somerville, a 3 bedroom for 2300, so I paid 750 a month, and that wasnt bad.