Cost of self-managed homeownership

Building permit with plan
Electrical installation

And when do you want to complete the few thousand working hours?

Hopefully the other numbers are better estimated. Windows and doors don’t fit

There is a channel on YouTube called "The Crazy Framer" who built a 200m² house by himself. It is a bit American, but overall very inspiring. The question is ultimately how much one can accomplish alone.

Thought too much Konny Reimann

As you know, triple glazing is not the same as triple glazing
You are aware of which documents and proofs you need for the building application and can prepare them yourself
You accept missing insurance coverage and your energy provider carries out the house connection?

I assume that you have dealt with the advantages of floating screed and the difficulty level of the Swedish floor slab

1x1 windows are loopholes

Do you own a plot of land? The building regulations will ruin your plan. If money is that tight, I would rather stay renting. If it's the project itself that matters to you, then just build a garden house.

The building regulations will ruin your plan

That was exactly my first thought as well. We are in Germany.

Thank you for your reply! I am personally still at the very beginning, in a phase of orientation and idea finding. Unfortunately, my budget does not allow for more, and I don't think banks finance self-built houses because there is no warranty. The rental apartment I live in does not have large windows, I feel quite comfortable, maybe I can save energy through the size that does not come from top quality, although none of this is certain. I could also spend 25 percent more on all items. Actually, I do not know the exact official procedure, but I hope that the structural engineer in the family can help me with this and also create the plans for me. Otherwise, I am really grateful for any help and constructive criticism. I personally find it a bit unfortunate that one is immediately confronted with so much "frustration" with off-topic comments, like the thing about chips and beer.

Do you have a plot of land?

The plot of land is not the problem. There is no development plan.
Of course, I plan to comply with all building regulations
or to seek advice on that. I also do not rule out
an architect.
The prefabricated house builders who work with timber frame construction
basically do nothing different, do they?