Viktor,
My suggestion is to drive each of these places and see the proximity of them to where you do your normal activities, work, family and friends. Then see if you like the feel of the location. Do your math and see if you can make the math work with places on the MLS. Next, find a realtor who works with investors and can give you the support, not just during the search, but after you own the property, with local contractors, zoning and permit review. And, make sure that you get a full tour of the area that shows you where the traffic patterns are. Where the major places of industry are, and where the grocery stores are. That way you can understand who your tenant will be and how they will live their daily lives. Where they will work, shop and entertain themselves. Find and agent who understands rents, and the local economy. Then work with them to figure out the best place for you. In Worcester if you check the deed recordings at the end of each week you will see that about 1/3 of all multifamily properties are trading off the MLS. A Good multi-family/ investment realtor has access to these deals on a regular basis and will be able to help you navigate the process.