is there any lease involved?
and for them to terminate their lease before time, it is sometimes required that those moving out, find someone to replace them and take over their lease.
do you pay rent separately? or is it all one payment as a whole. if its seperate, you shouldnt be required to pay more rent than you already are..... the bills tho can be a tough situation tho. whos name is on the bills? if its one of your roomates, they will have to take it out of their name... depending on where you live, there is also laws that sometimes categorizes people who reside in a house for more than a 30 day period, responsible for bills and such, even if there is no paper lease. same goes for if someone wants to kick someone out of their own home, once certain criteria is met, the person would have to goto court to evict the person from their home even tho no lease was created.
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disclaimer: there are quite a few "tapp-o"s while using my phone. if i dont recognize it, and if it doesnt seem to make sense, then the chances of it being a tapp-o (typo) are very high.
*currently using iPhone 4*