Financing check - realistic or nonsense?

Do not see this as realistic. Even with the very low estimated construction costs, it doesn’t work. And they will still rise significantly. Since you only have one income, you will exceed the loan amount = 110x net salary rule. And that is actually already the pain threshold. In addition, you have saved (too) little, 50k is practically nothing at your age.

I am a bit confused: you don’t get subsidized cash in hand, do you? Please clarify for me, e.g. , I built in 2013.. back then there were KfW subsidies through percentages… Regarding the rest: incidental construction costs are underestimated. And about the garden: do you want to fully develop the 1600 sqm? Usually one plans an orchard meadow, but not a designed promenade garden?! The fundamental question: with €3600 no bank will give you a loan for an oversized house. Anyone who doubts whether they can afford a house should simply plan a house that is financially possible and not become megalomaniac right away ;)

As I understand it, there is a repayment grant after completion of the house – here €37,500 per residential unit. However, the correct – and here I actually still have an error in my calculation – is that you do not get “another” €150k loan per unit, but the €37,500 is deducted from the loan amount after the house is finished. Therefore, that must be added to the debt capital. Megalomaniac – that’s what it’s about for me, to get a feeling about what is megalomaniac and what is not ;)

With your income, I would rather look at existing properties.

In the constellation of planning, especially size, hillside property with corresponding additional foundation costs, and your household net income, you must and should discard this planning and better reorient yourselves. New construction will probably already be rather tight.. in which region do you want to build?

200sqm including basement on a hillside with a 3.6k€ income is crazy. Above all, the children are still missing.

Ask yourself why the GUs don't tell you that it won't work.

Our house is located at the back on the slope. On the right and left sides of the house, the terrain slopes down to the yard/driveway. The area in front of the house does not need to be leveled? 300 solid ground? Or already loosened. Just ask the next landfill how expensive unloading is. There can be nasty surprises.

But it doesn't really matter. I find your planned financing so far simply harakiri. 3.8k income and 465k loan is an absolute mismatch. I just can't put it any nicer. I'm shocked if a bank agrees to that. Children will (in the future) also cost you money.

And the fact that your cost estimate is incomplete is obvious even to common sense. How high is your budget for upgrades beyond the standard construction description? And then every builder also needs a buffer for unforeseen expenses. I don't see any of that from you. The house will be built and the 100k budget for the outdoor facilities will be gone. And then how do you want to save on the outdoor facilities that, as you have already noticed, are no bargain on the slope?