If you are looking at homes in Brockton, the Assessor's office has made it's database available online. There is a wealth of information there, including a sketch of the footprint of the home. Many other South Shore towns have similar information available online as well. If you Google "Assessor" and the name of the town you are interested in, you should be able to find out if that town has put detailed information on line. If not, you may have to visit the Assessor's Office (usually located in Town Hall) and ask for a print out of their "field card" for the property you are interested in. Some towns will charge you a nominal fee for the printout.
I've included a link to the Brockton Assessor's database below.