Q: I share an apartment with a roommate and we generally split rent, utilities and telephone. If I was away for most of the month, do I need to share in the expenses equally?
A: This depends on the initial agreement and the common practice. It is typical that one roommate might use the apartment more than the other. For example, one may go away for Shabbos frequently; one roommate might take vacation this time of year and the other at a different time.
Thus, if the initial agreement was to split the expenses without any exclusion, you would be liable to pay your half even while you are away. This applies not only to fixed expenses such as rent, but also to expenses dependent on use such as utilities, unless there is a clear common practice to the contrary, or the roommate willingly agrees to pay a larger share this month.
Furthermore, you are not allowed to have someone replace you while you are away without your roommate’s consent to that person, unless your initial agreement states otherwise (C.M. 316:2).