House construction / house purchase planned, evaluation of financing plan

Is the calculation that unrealistic?

It could roughly be correct. It's just under €2400/m², which should be realistic. Who pays for the garden? The home construction company? And what services are included for the garden? Metal garages sometimes have a bad reputation regarding moisture. However, I don't know if there's any truth to that. If I were you, I would definitely get more information on that. But €10,000 sounds realistic; I had similar offers. Although the offer from Rekers for a concrete garage wasn't more expensive either. Three installments for the house seems too little to me. You will probably massively overpay in between.

Could be roughly correct. It's just under 2400€/sqm, that should be realistic. Who pays for the garden? The house construction company? And which services are included in the garden? Metal garages sometimes have a bad reputation regarding moisture. But I don't know if there's any truth to that. If I were you, I would definitely check on that again. But 10,000€ sounds realistic, I had similar offers. Although the offer from Rekers for a concrete garage wasn't more expensive either. Three installments for the house seems too little to me. You will probably massively overpay in between.

We are getting the garden sponsored by the family. I just looked again in the contract regarding the payments: 5% after submission of the building application 75% on the 4th construction day (as mentioned, prefabricated house) 10% after screed installation 10% after completion / handover Duration of construction at the current point in time: 23 weeks from the creation of the foundation slab.

Metal garages partly have a bad reputation regarding moisture. But I don't know if there's any truth to that.

There is little truth to that. We have 3 of them and are very satisfied. Normally, they are sometimes better ventilated than a stone garage because air comes in between the roof and the wall through the trapezoidal shape of the roofing. Only occasionally do we have a few drops on the roof that might sometimes drip onto the car, but that doesn't harm any vehicle. And we even store suitcases and backpacks, decorations, car accessories in there, and that causes no problems. They are inexpensive, easy to set up, and you can even buy them used. For the foundation, deep borders are sufficient, and inside you can cheaply pave if you like. And you can also color them however you want.

5% after submission of the building application 75% on the 4th day of assembly (as mentioned, prefabricated house) 10% after screed installation 10% after completion / handover

You have a large sum of money that will cost you 3% at most until the assembly date in case of doubt. For the rest, the commitment interest is then relatively manageable, but I would try, if possible, to still schedule the assembly date within the commitment period (or factor it in fixed when comparing offers).

So, I am speaking up again after a long time. In September (yes, everything is taking a very long time) the notary contract for the property was concluded. Real estate transfer tax and land registry fees have already been paid, I am still waiting for the invoice from the notary. The development area is still not developed as of today, there are not even construction roads yet. However, these are supposed to be completed later this year. The financing was arranged through my house bank, consisting of three components (2x KFW and the rest from the house bank). Since the contract was only signed a month ago, commitment interest will only be payable from October 2022. Before that, of course, interest on amounts already withdrawn. I find the conditions quite good for 100% financing, 1.35% effective interest with a repayment rate of 3.08%. The monthly rate is around 2100 euros.

The conditions are quite good for a 100% financing, 1.35% effective interest rate with a repayment rate of 3.08%. The monthly installment amounts to around 2100 euros.

For understanding: The total installment (1xBank, 2xKfW) amounts to 2100 €. But interest + repayment refer only to 1xBank, right? What volume, what fixed interest period are we talking about here? The numbers cannot be evaluated as they are.