> My definition of decent is any area that is generally safe, and that is within walking distance to the subway. It does not have to be quiet; I don't mind being in a lively area. And I don't want to deal with rats and cockroaches. Nothing outlandish.

First, most areas that are walking distance to the subway are generally safe, and clean. So what comes down to is where you work that will decide the best spot to live.

> not be able to get anything decent for $2,700

There are plenty of great places for under $2700, stop looking at the newly built "luxury" places. Check /r/bostonhousing

> rent is the main thing that sucks money in Boston

It is. Save more money and get roommates if you want, or give up on the 40 min commute idea to save more. But at your salary you will be fine.