Q: I have one roommate in a 2 bedroom apartment. About a year ago, he started dating a girl. He has said that he does not want her to move in right now, but for about the past two months she has been staying at our apartment every night. Is it proper to start asking her to pay rent, etc?
A: No, but you do need to talk with your roommate and tell him that you like his girlfriend very much, but that your agreement to live together did not involve other people moving in with you, and you are uncomfortable having her there as a permanent guest. You can ask him his intentions, and if she is going to move in, and you don’t mind, then you and he need to talk about expenses. You can talk about sharing the rent three ways instead of two, if you feel she or he should pay her way and her presence is constricting to you, but a rent reduction would make it easier to put up with her presence. You also would need to talk about sharing utilities differently, because regardless of who pays the rent, another person increases electricity and water use, certainly. It may be that you and he share consumables, from food to toilet paper to paper towels, that she is using, too, therefore making their combined use two-to-one and causing you to be paying for her consumption. This is something that needs to be discussed by the two of you rather than by you and his girlfriend. IF you agree that she can be your other roommate, then you need to have a group “meeting” about how you are dividing responsibilities, including financial ones.