I feel really confused and stupid not to understand this.
If there is £200k equity and £100k mortgage and I give ex £100k and take on the mortgage, am I giving him £150k or £100k?
If we were selling the house we would pay off the mortgage with the proceeds of the sale. In this scenario, I'm taking my equity and choosing to take on a mortgage to buy our house instead of another one.
Am I missing something?