@Oye Dosumu Malden is not a bad area if you target near Malden Center or Oak Grove (near a T stop) you'll do fine. Malden does have really high taxes as well but if you are using the property as your primary residence, you will qualify for a Residential Exemption. It changes every year but you can qualify to reduce your property taxes significantly if you live in your investment property.
This also applies in the city of Boston. Make sure you contact the city to find out the percentage of the Residential Exemption. I never use these exemptions in my numbers because I always take into account when I relocate and still own the property purely for investment.
You can still find deals in Mattapan. Again, if you stay close to the 'T', you cannot go wrong. Young professionals are always looking for apartments near public transportation and Mattapan is on the Red line. Granted it's a high crime area, I predict it will get much better in a few years. As a friendly reminder, there will always be a risk predicting the next hot spot.