Construction cost estimation of a semi-detached house experiences

My wife works part-time for minimum wage. But she likes the job.

That's where I would start. At the moment, the full risk of a high financing rests on a single earner, and that in sales. I also had to calculate for my wife that the dream of a house will only not turn into a nightmare if she says goodbye to a comfortable life in low part-time. She now works 75%, finds it too much, but sees what it is for.

Yes, I agree. Financing €700,000 would really be a tough nut to crack. Even if my wife were to earn more now , we would then lose the KFW funding in reverse, since it is limited to €90,000 taxable income. That in turn would increase the interest rates. Even working full-time at minimum wage in tax class 5, only about €400 net would be added. That would make €5,300 per month, about €1,950 loan repayment. That would also likely not be enough to manage such financing. This means either significantly increasing income and losing all subsidies, or raising additional equity and taking advantage of the funding, alternatively building with QNG, which would bring €270,000 instead of €170,000, but would also significantly complicate the construction project. According to my calculations, in such a case we would definitely need €7,000 net per month to be able to manage the project. Difficult.