Taking over half a mortgage

ksjohnson

My girlfriend owns a flat with her sister. They now want to sell. However, they've been told they'll need to sell at almost a loss in order to get rid of it. My girlfriend is not keen to do this and wants to hold on to it for a few years, her sister wants to get rid of the place no matter what.

We're thinking of looking to put me on the mortgage, effectively buying out her sister. However, we don't know how easy and more importantly how costly this will be. In terms of monthly outgoings, I could afford the mortgage that her sister pays, and she doesn't want anything for it. However I couldn't afford a deposit etc, so how much would we be looking at paying to put me on the mortgage in her place? And is it that difficult? Mortgage is with HSBC. I have no mortgage, kids or any commitments as such.