So I signed a lease with my roommate, lets call her kelly. Kelly and I both had to have cosigners for our apt. Now, Kelly, has ducked out on the lease, which has 6 months left and left me to pay the entire rent, which I can't afford. Can I sue her cosigner for the rest of rent? And if so, is it under small claims court, or something else? I live in Massachusetts.

OK, you and "kelly" signed a lease. So your landlord can sue you, sue kelly or sue either of the co-signers or heck sue all of you.

Now what was the agreement between you and her, do you have a written agreement as to who pays what.

And the other problem is that only the landlord has a legal agreement to the co-signer. The issue I see is that you have no legal agreement with the co-signer, most likely only Kelly promised to pay you 1/2 of the rent, the co-signer only promised to pay the landlord if no one paid.

Now with that said, I would sue kelly and the co signer in small claims court, it is possible the co signer will not be held liable to you. If you don't pay the landlord, then the landlord could sue them.

Also a side note, since each of you had a co-signer did you sign the lease for the entire amount, or merely 1/2 each