A word of caution, always be sure to check with the building inspector of the city/town when you find a property (and Don't just rely on the Listing Info). Confirm with That Authority that the property does in fact 'qualify' as an In-Law apartment if it is important to you. You may be surprised at how many don't.
Most of us realtors have an MLS assistant program which will send you listings: new to market, price changes etc. BUT the catch is that you sign up with a realtor. If you just want to "look" and not make any commitments, go to http://www.realtor.com - there you can put in your town and price range, Bedrooms etc
It is improper for any realtor to attempt to solicit business on this forum - (according to our Community Guidelines) - we are ONLY here to give advice. Good luck with your search.
I live and work in the Merrimack Valley and North Shore area, and I think you would find it perfect. The area offers an easy commute, as it is surrounded by 3 major Boston commuter routes, and just about every town has a commuter rail station. It's a lovely area with quintessential and SAFE New England neighborhoods. It's a quick drive to the beaches, to Boston, and to skiing, and best of all it's AFFORDABLE!
I publish a Homes & Land Magazine for that area, we have a few thousand listings on our web site that you may want to check out. http://www.HomesAndLandMA.com. Or I would be happy to mail you a copy of the next issue, just let me know! Best of luck with your search.
Homes & Land Magazine
If you can provide some more parameters (areas of MA, price range, etc...), I'd be glad to set you up to automatically receive appropriate listings via e-mail. Unfortunately, most of the consumer property search sites do not let you search by keyword criteria. They just don't drill down that deep. The MLS interface that we Realtors use does allow this and this might be the easiest way to identify the properties you are interested in. Let me know if that would be helpful and I'd be happy to set it up for you.
All My Best, Mike.