First of all, I would like to be polite and thank you for the responses given!
To be honest, I am somewhat shocked by the answers. Not because there were no "desired" answers as such. No, it is the assumptions, sometimes even insinuations. I wonder if this is really necessary.
Admittedly, at first glance my question may look like a "crazy idea." I come from the Rhineland, and here there are sometimes houses from €30,000, with plots from 500sqm (in the case of foreclosures usually considerably cheaper). That these properties then require certain investments is, I think, undisputed. Ultimately, it would need to be examined on a case-by-case basis which investments exactly. The question is always: what do I want or what is sufficient for me.
As already described in my question, I am not unskilled in craftsmanship. That the result is not always equivalent to that of a true professional is, I think, also clear (although there are also professionals who do not work very precisely. However, that is another matter).
If I did not have a few such cases myself in my (extended) circle of acquaintances, I would accept if you assumed a certain lack of judgment on my part. There financing without any equity capital has worked easily. A condition was sometimes that existing financing had to be paid off beforehand (for example, by a loan from mother/father/uncle/aunt).
Why, how, and for what reason it ultimately still worked with the financing could probably only be revealed to me by the responsible caseworker.
A good year ago (the situation was identical, only the employment was still temporary) I inquired "superficially" at a credit institution. There they saw the possibility, for example, of a building savings contract. However, an acquaintance strongly and directly advised me against it. Due to various private events, I also put the matter on ice again.
In conclusion, I would like to add something: In my opinion, personal circumstances also play a considerable role. If someone is indeed frugal (equity capital of €5,000 was available until about 6 months ago), does not lead an extravagant life, partly provides for themselves, then €2,100 (or soon €2,400) for one person is quite a decent income.