I have owned my house for 10 years. My boyfriend has been living in it for nearly two years. So far he hasn't been paying anything towards the mortgage. We split bills and council tax 50:50. This suits me fine, but the point of the arrangement was so that if living together didn't work out, it would be fairly simple for him to move out and me to keep my house. Now it's been a while and nothing has gone horribly wrong, and it occurs to me that while most of my savings are invested in a nice house in a pleasant part of a densely populated city, most of his savings are in a savings account that isn't really making much interest. The fixed term of the mortgage is coming to an end soon, so I will have to go to a mortgage review anyway. Perhaps I should be nice and offer to let him in on the home ownership.
My boyfriend is trustworthy but we are not married or engaged or anything so the relationship could end at any point. If he starts paying money onto the mortgage, will the house just suddenly belong 50% to him? Or is there a way of letting him in on the ownership gradually, in a way that would be fair to both of us? I would have thought this was a fairly standard thing, but I haven't found any formulae for how it could work. If I pay £X per month and he pays £Y per month, how could we work out what percentage of the house he owns at any given point?
I have got the mortgage to below 50% of what I originally paid for the house, but I am still concerned that if he moves out I would not be able to pay him 50% of the house price without selling the house and moving out myself. I like my house and while my boyfriend is more important, I'd really rather avoid losing both.