Feasibility financing new construction (land + semi-detached house or semi-detached half)

realistic house price

This is always forgotten here. Those who want to calculate this as feasible: take a look at which costs were calculated and what is realistic, those are worlds apart, if not universes.

Or the 3 children go to study in 3 different cities and each needs an apartment. Financially, children are only independent in their mid/late 20s

Aside from the fact that this would also be a problem in the case of a rental apartment (as already mentioned by ), this is completely unrealistic for the vast majority of the population. Who can afford to finance apartments for three children in three different cities? I commuted a total of three hours daily during my Bachelor's degree and had a mini-job on the side earning €450. After graduation, I started working full-time and saving money to later be able to do my Master's abroad. And this is certainly more the rule than the exception. I hardly know anyone who had an apartment financed by their parents during their studies. So I would simply exclude such scenarios. There is probably also a university in Stuttgart, and you can always move to another city or country later once you have saved your own money. You might just have to make compromises with the house as well. This is of course an outdated extreme example, but my mother had to live without a bathroom for months as a child because my grandparents ran out of money during the house construction. The house still exists today and is still inhabited by the family. Of course, you can no longer live without a bathroom nowadays, but maybe you can at least leave things like the landscaping aside for now, get a (used) Ikea kitchen, etc. As already mentioned, if the OP soon needs a bigger apartment, he will have to live very frugally anyway. In the case of a large rental apartment, he probably won't build any wealth on the side and will be much worse off in old age than with the semi-detached/semi-detached house on municipal land solution. And even if he has probably already decided, the thread might also be interesting for others who are in a similar situation.

You assume that a cheaply built house on expensive land will be worth a lot in 20 years. I would put a big question mark on that. Especially the Stuttgart area, with its dependence on the automotive industry, has a high potential for problems due to structural change.

Even if so, the house contains €200,000 in city subsidies and €80,000 in equity. That can cushion a lot of hypothetical value loss over 20 years. So normally I’m usually the type to have doubts and always advise against buying a house when it gets tight. But in this case, strangely enough, I’m still in favor of taking the risk. With borderline constructs like under 2% repayment, it could somehow become doable. Many small things speak in favor: high equity, discounted land, all the children already there, 38 years until retirement, lack of rental alternatives, reflective appearance, etc.

In the case of a large rental apartment, he probably won't build any wealth on the side and will be considerably worse off in old age than with the semi-detached house / detached house solution on municipal land.

Why do you always believe that owning a house automatically builds wealth? Realistically, the subsidized land is the only thing that truly promises an increase in value. The house wears out over 20 years and requires renovations. Realistically, only a repayment slightly above 1% is even possible (creditworthiness aside), but that means that almost nothing will be paid off in 20 years. From the low repayment, one must honestly still deduct renovation needs, because there is no money for reserves. However, with the "berserker-saving" option, wealth can also be built up in 20 years even in the expensive rental apartment. Just the 80k equity invested in the stock market yields quite a bit.

Of course, you can't live without a bathroom nowadays, but maybe you can at least skip things like the outdoor facilities at first, get a (used) IKEA kitchen, etc.

Doing things later only works if you have a decent monthly surplus. Here, there simply is no budget to do anything later. With 100€/month you can save for the paving stones for a long time.

Even so, the house contains €200,000 subsidy from the city and €80,000 equity. That can cushion a lot of hypothetical value loss over 20 years.

I don’t see €200k subsidies. That is simply the poster’s estimate. And it basically comes from the selling price of existing houses and the supposedly low construction costs of his project. But as has already been shown, that does not add up. The total costs will certainly not be under €700k, and then €800k value is only a €100k difference. The land is called subsidized at €300-500, but I would question that claim critically if calculating tightly. I specifically took out the land value map, where the area is listed at €780. I’ll give it €1000 now, then we come to about €110k subsidy, which also matches my calculation above quite well. Whether it would really sell for €1200/sqm... People who would spend half a million on a plot are not typical townhouse builders. Incidentally, also not the typical buyers for townhouses from Allkauf Haus.

I don't know why everyone thinks that 20-year-old houses are ready for demolition or at least need renovation costing 50% of the purchase price, and therefore the houses are worthless. As long as there are 50 applicants for every building plot, single-family houses will increase in value in the coming years, even those in which nothing is invested. Of course, of the 50, surely 10 are those who can't get financing or want to build only in a few years, but there are also 10 who would pay double the price per square meter without batting an eye.

Normally, I am usually such a worrywart myself

That's true, which is why I am all the more surprised about this from you:

it could somehow become doable

and I am therefore taking the liberty once again (sorry) to point out the assumption of the OP:

Turnkey with basement 270,000 EUR

in Stuttgart. With basement. "Turnkey".