I can understand why you see this obligation as an emotional obligation. It is is tie to her that really is unnecessary at least emotionally. As far as buying a house, I would make it known that you cannot get the house of your dreams, if he helping to pay her mortgage. Not only is this expensive its inappropriate. And as long as this house is around so is she. I don't understand why your fiancee would not want to encourage total independence on her part. Paying half the mortgage because she isn't ready to sell is barely tolerable. But paying it and enabling her is just plain silly. Try to explore the reason for his continuing this expense. Sometimes people remain in unnecessary financial obligations it is really from some other emotion - such as guilt. Try to get him to discuss and separate emotions from money. Unless there is something else, I am not getting it either