That would be an idea too, but I don't want to pay off the place forever and I also want to get rid of the 75k.
The term has nothing to do with the loan amount. Besides, there are two of you – not just your decision. And you can invest the additional 50k better than putting it into the house. Should you separate – everything is perfectly arranged. Should you get married, you just add the 50k later into the financing (as a special repayment or at the interest expiration) – also perfectly arranged.
But please always remember, it has to be decided together. You alone do not determine. And a proportional split is always rubbish, even with a contract.