Hi, I think it might be a good idea if he got his property valued and she buys out 50% when she gets her flat sold , that way it would go into joint names and should anything happen between them, a break up or even death as none if us know the day , then she would be entitled to half of the value. By just handing him money to pay off HIS mortgage she has nothing to show for her money. I certainly would not give my money over , if married maybe but living together no!! I live in sin myself and have done for 20 years but we live in my property and my solicitor got him to sign that he does not have an interest in it. He has no problems with that. As I am not intending to have a family I am not worried about marriage but if I was young and wanting to have a baby I would definately want to be married and with the house in joint names then there would be the child to leave her share to in later life too which makes it all easy. They could afford a small wedding if she buys her share as he would have some money from that. I hope it works out for her soon.