The other thing to consider is, depending on the number of years you have been paying a mortgage, you might hav contributed apt to the ownership of the house without actually having any rights to it. If you stay in the arrangement for say 10 years and then split he would still remain the owner of any capital paid off the mortgage and you would be left with nothing. Similar to if you had been renting so not necessarily the end of the world but something to consider.
Whilst l living there for two years does mean you have some cohabitation rights it can be easy to spend thousands going to court to not have them upheld depending on what the judge feels so it isn’t as secure as it may feel. X
I agree with your mum. I moved out of my rented house into my partners owned house. I went 5050 on all bills EXCEPT the mortgage. I put the money I would have spent of rent/mortgage in savings. When it came to having children and buying a bigger house, we had very similar amounts to go towards the deposit on a joint mortgage. So now I do contribute. I pay half of the mortgage, but then he pays all the rest of the household bills and I pay for childcare and the car. Which is basically 50/50 anyway.
I think it depends what he is doing with his extra income. If he is saving some of it and it would be used towards your future as a family then I think that’s fine. If he just spends the rest of his money on whatever he wants whilst you are trying to save toward your future then I’d say you could split just the mortgage by earnings. Realistically, if you buy a house together once you’ve got deposit money, then it won’t matter anyway, as the money he has put toward the current house will go in with yours and it will be your house too. So long as you’ve lived together at least two years and you have contributed to the mortgage you have legal rights to your home even if he is the sole legal owner. A lot of people don’t combine finances until marriage. I wouldn’t split hairs over it if you were both happy and you are both working toward a future and a home together. I definitely wouldn’t consider renting as that doesn’t make financial sense.