Roommate Leaving Early Will Cost Me Money - What Can I Do

[umichgoblue83]

My question involves a roommate in the State of: Michigan.

I signed a 12 month lease (August to August) with my roommate. When we moved in, it so happened that her girlfriend moved in with us also. This wasn't part of the initial plan, but we talked about it and agreed that we were all okay with the situation and that instead of splitting the rent 50% me and 50% for the two of them who are sharing a room, I would pay 350 per month, one of them 200 per month, and the other 300 per month. Recently, they decided that the living arrangement is no longer working for them and have decided to seek a subletter. They gave me no official time-line for the process, but have obviously been considering this for some time as they stated that they were saving up their money to do this. Are they required to give me at least 30 days notice? I'm not prepared for this financial shift. They did, however, offer to let me have some say in who they choose to take over. By them leaving, my rent will be going up $75/month which will cost me a total of $525 in the end. Since we never put this arrangement in writing (it was a verbal arrangement), do I have legal recourse so that I don't lose money by them leaving early? I have cashed several months of checks from them showing this arrangement. Further, there was the expectation that they would see the lease through full-term. What can I do to not lose so much money? Do I sue them both in small claims or just the one girl who is actually on the lease? If I sue both, do I split the cost equally? Please help!!!!