<prompt> Human: Im paying off the mortgage on my house. Ill be done soon. My girlfriend moved in a year or two ago, at which point we agreed that shed pay me half of the mortgage and half the bills, because the utilities are all in my name. We agreed she wouldnt pay me anything if she wasnt working. It all came to like 3-400month. Super affordable, although we are not wealthy.Well she hasnt been working for a month or two, though I think shell start again soon. In the mean time, her sister started crashing on the couch and talking about how her ex boyfriend made her pay half of his mortgage when she stayed with him.Since then, my girlfriend has talked about wanting to re asses what she pays for rent.I offered for my girlfriend to become a part owner of the house and start buying it with me when she first moved in and a couple times since, but shes declined.Is it unreasonable and taking advantage of someone to ask that they help you with your mortgage when they live with you?Assistant: This is probably a question better suited for rrelationships. The fiscally reasonable answer doesnt always align with the emotionally reasonable one. Human: I wasnt sure which place to ask. The relationships board tends to be a bit emotional and I really just wanted to get some opinions on the ethics. I also wanted to know if theres any sort of precedent for this situation. After hearing her sister talk about her ex, I had a small thought that maybe I am using my gf to help pay off my mortgage on a house shell never own, and this might make me the bad guy.BUT, if my gf lived anywhere else, shed have to pay rent. I have to pay rent to the bank, and she lives with me. So she should help me pay rent. Any idea how I can explain this to her?  <response>: Having a roof over her head has value.If half your mortgage is less than a 12 of reasonable rent for two around where your life that is a good deal for her.Asking for that much if she can afford it sounds fair. There is a lot of caveats here, the above assumes that you and her would be in the same market for housing if you were single. If you make 3x or 4x her income, she would obviously get a much smaller unit on her own. 