The apartment is in Dorchester, at 10-15 min walk from the red line. There are also buses nearby, so it's well connected with the center and Cambridge (35-40min to MIT). The house is old but nice. If there is any problem, Marie will help you as soon as possible, no matter the week day.
I listened some people had problems in the neighborhood because it could be dangerous, but I personally didn't have any trouble, even when it was quite late in the night. There are supermarkets close with a good price. In general, it was great and it's one of the cheapest options in Boston for a long stay