Each 4 credit pre med science class is $850. That is not including registration fee or books. Specific costs for other classes are on their website extension.harvard.edu under the courses section.
Housing depends on where you live in cambridge, if you plan on living with roommates, etc. Go to boston.craigslist.com for housing costs.
Obviously, sky's the limit. As for the low side, One can live as cheaply as ~$1000/month with enough planning. My rent is only 450, I take the T everywhere ($40/month tops), and bills are split 4 ways to get it down to $50/month. That leaves about $15/day for food, which can be done only if you cook at home (lots of pasta, etc.). I was close to that at the beginning of the semester, but time constraints force you to eat out a lot more often.
It doesn't hurt eating 4 free meals a week @ Mass General - stock that belly FULL. 🙂
Tuition is cheap - also remember health insurance - that's $1300/semester but is fantastic coverage ($10 copays on drugs, none on visits for me so far). Aside from that, YMMV - x-mas presents weren't cheap this year - if everyone was in the giving spirit they'd give themselves a diet book and save me money. Oops, that slipped out.
