Keith, you said that you are based in Cambridge, do you know the area well? Have you been here a while and know the market?
My family owns and holds 24 units in Cambridge that I manage and lease along with many others. We also buy, Reno, hold and rent other properties in Somerville and Medford too. The buy and hold strategy is ridiculously safe in this market. Universities such as MIT, Harvard, Tufts, etc. and Hospitals such as MGH, Beth Israel etc. make this market incredibly stable for landlords with high end tenant turnover and cash flow becoming routine.
These days the trick is having the financial ability to invest in this market which is crazy competitive. Not only that is being able to find the deals which are quickly dealt before they hit the open market like MLS.
There are other outlets to find these opportunities if you know where to look. Check out Boston wealth builders. If you ever have any questions about the area myself and everyone else on bigger pockets in Boston is here to help, welcome!