Resident Tax Exemption in Somerville

[smoterh.livejournal.com]

Hi there,

I bought a two family last April in Somerville and I heard that if you reside in your own place you get a tax exemption or something like that.
Two questions - does anybody have any ideas on where I can find info on residential tax exemption for Somerville?  Second question is how is this supposed to work on a 2 family property where I live in half of the whole house.  I lied, third question, how can this all be worked out when it is my mortgage lender that pays my taxes to Somerville.

Thanks
Hugo