Finance the property now or continue saving equity?

. Here there are speculation tax and real estate transfer tax and notary fees and so on and so forth.

Speculation tax used to exist in Germany for stocks with short holding periods, but never for real estate. And taxation on the profit does not apply to owner-occupied property. In the USA there is no real estate transfer tax, but property tax of up to 2% of the actual value, and not like here previously an assumed very old value. Notary and two times broker fees are also not free in the USA.

Speculation tax used to exist in Germany for stocks held for a short time, but never for real estate.

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It still exists today for real estate with a short holding period, provided they were not exclusively owner-occupied.

It’s about the specific situation of the OP, and if I know from the outset that I might have to sell again within the first 5-10 years, then Germany is not the ideal country for such a construct. Because both in construction/land acquisition you incur enormous one-time costs, as well as upon sale.
Even if these only partially occur again when selling (notary, for example), one must still consider that potential buyers pay a lot of real estate transfer tax on the entire property, not just on the land. And this indirectly reduces what you can get for the house. Because buyers usually have only a certain budget X, and that must cover the house price and ancillary costs.

With around 35,000 stationed US soldiers in Germany, most of them enlisted ranks, for whom property is in any case out of the question, is

at 7,000 net/month he is certainly not a simple soldier. Although not even the question was answered whether he is a soldier at all. Soldiers can retire after 20 years, which he could have achieved at the age of 41.

No, actually the exact opposite is the case. For the bank to finance you, it wants to see relatively detailed what it is actually financing.
That means you need a calculation from the builder or architect, floor plans, section drawings, etc.
Z

It was completely different for us. I went to the house bank, we discussed the basic data, and then the financing was clear at first. After a few months we found the property, made the contract with the bank, and that was it. After a few months we submitted photos of the renovation, that was enough for the Sparkasse.
The financing was significantly easier than finding the right house.

It was completely different for us. I went to the house bank, we discussed the basic data, and then the financing was clear for the time being. After a few months, we found the property, made the contract with the bank, and that was it. After a few months, we submitted photos of the renovation, which was enough for the Sparkasse. The financing was much easier than finding the right house.

That is the case with existing property purchases. If you build new, you usually have to provide the documents mentioned with the specific financing request. The only thing the bank may give you beforehand is a "financing confirmation," but it is only worth as much as the paper it is printed on.