Here is the link to the Somerville proposed zoning changes: https://www.somervillezoning.com/If you read through everything carefully it basically looks like they are proposing that if you have a large enough lot size or enough frontage you can build an "accessory dwelling" behind your house. 

I will bet they'll come back with you can add an accessory dwelling unit which in my opinion isn't worth it.

Here is one definition I copied: "A criminal charge of aiding and abetting or accessory can usually be brought against anyone who helps in the commission of a crime, though legal distinctions vary by state.

You need to search for "Accessory Dwelling"  For example "Herriman Accessory Dwelling"   That will usually get you what you need.  

The only county that now allows tiny homes as secondary "accessory dwelling units" (ADU) (when there is another, bigger house on the property) is Fresno.Tiny homes on foundations have other problems.

We recently finished putting in an accessory apartment (in-law apartment) which my sister has moved into.

Are you building a new structure as well or is it an existing accessory building? 

( accessory dwelling units)!!!

I am curious how you were able to get the accessory swelling unit permitted?

It's a side accessory to the solar panels, so they won't do just that component, but it does show that there are private sector (eg, no big gov't process & 'official' meters not needed) solutions to this.