Buying a House with Partner Advice

getmore4less

To work through the other proposal with shares owned 75% 25% with  you owning the debt.

So in Year 1, ok so nobody's choosing to sell now, but say you've had some crisis and need to sell for whatever reason. You've paid maybe 5k off the mortgage, house is same price, so equity is £455k.
correct answer £450k £5k
Option 1 your partner will get £341k back, you'll get £114k.
Option 2 your partner will get £450k back, you'll get £5k.
Option 3 your partner will get £451.25k back, you'll get £3.75k
Option 4 partner = £450k, you £5k

Now let's look at Year 10. Let's say you've paid 50k off the mortgage, and the value of the house has risen by 20% (120k). So your total equity is 620k.
correct answer £540k £80k
Option 1 your partner will get £465k back, you'll get £155k.
Option 2 your partner will get £450k back, you'll get £170k.
Option 3 your partner will get £492.5k back, you'll get £127.5k
Option 4 partner = £510k, you £110k

And now let's look at Year 25. You've fully paid off the mortgage (150k), and say the value of the house has risen by 80% (480k). You now have 1.08m equity
correct answer £810k £270k
Option 1 your partner will get £810k back, you'll get £270k.
Option 2 your partner will get £450k back, you'll get £630k.
Option 3 your partner will get £607.50k back, you'll get £472.50k
Option 4 partner = £690k, you £390k

mlz1413

You need a solicitor to draw up an agreement of how proceeds are split, this is regardless of if it is because of a sale or because of a death. 
As said before the borrowing would need to be in joint names so you will need an agreement in place for that too.  
I'd also think about what happens to the house if you die first, are you happy for your 25% share to go to your partner or do you have family that you want to benefit from your estate? 

getmore4less

The mortgage does not have to be joint, for this case not sure it add any benefit.

HSBC will do joint proprietor sole borrower mortgages,
They also do lending where the borrower is not a proprietor there was a thread on here about it.