As already mentioned, changes in repayment are usually possible and special repayments are actually included in almost every financing. But of course, it is important to pay attention to that. If you can and it doesn't make much difference, fix the nominal interest rate for as many years as possible; after 10 years, you can legally switch to a cheaper loan anyway if the interest rates are lower by then. Otherwise, making special repayments does not always make sense, especially in times of high inflation. It is smarter to invest the money in ETFs and use it as equity in the follow-up financing. In the end, that can mean more capital overall. I personally am rather risk-taking and would try that in your position if you are a good team (which is not given in every relationship) and both are willing to tackle the project. Communicate well and listen sincerely to each other, that is the ABC. In the very worst case, you sell the house again in a few years; nobody has died from that yet. And you also have the prospect that the woman will bring money home in a year. A year goes by quickly and that does not feel like too many sacrifices in my opinion. A construction phase is usually similar and we all managed that as well. We were busy with our construction for over a year and had to manage rent + interest and all the other bills that came in at the same time. Vacations, etc. were not possible, but you know what you're doing it for. Now we have been living here for half a year and the time passed by very quickly. Especially at the beginning, you are busy with all sorts of things to make everything nice. However, that can also cost a lot of money, you must not forget that. And prepare yourself for a lot of stress. That personally affected me a lot. You must not forget to take care of yourself in between and also to rest sometimes. I completely forgot that until about a month ago when I was in the emergency room with atrial fibrillation. Well, lesson learned, now we're taking it a bit slower.