Financing as a self-employed person

And where it gets close to the limits, let the professional helper assist?

You whistle and... the professional only has time in 5 weeks... and for a small business he won't come anyway. So I wouldn't go around that naively at an advanced age.

You whistle and... the professional doesn’t have time for another 5 weeks... and for a small job he just doesn’t come.
So I wouldn’t go around so naïve at my age

Why so negative? Why do you accuse me of "whistling"?

Such a tone is disconcerting.

One thing is clear, you don’t buy a renovation project if you are timid, clumsy, or have two left hands...

Then you just go for turnkey, cookie-cutter solutions from the developer.

What excites me is doing it myself, thus also a hobby, where in the end it doesn’t matter if the bathroom took 3 times as long as a professional team would have.

My questions here were more about financing than about the assessment of my craftsmanship skills.

Why so negative? Why do you accuse me of "whistling"? Strange tone like that. One thing is clear, you don't buy a renovation project if you are not brave, clumsy, or have two left hands.... Then just go for turnkey cookie-cutter from the developer. What excites me is precisely doing it myself, thus also a hobby, where in the end it doesn’t matter if the bathroom took 3 times as long as a professional crew. My questions here were more related to financing than to the assessment of my craftsmanship skills.

Back to your question. Self-employed people are always difficult to place with banks. Your best chance is to get a loan from your business bank. Did you have a talk there?

I have my business account with an online bank, only the equity account is with the local bank. I found their offer unprofessional, no expression of modularities, "come by when you have auctioned the house," so only a verbal commitment of the credit line, nothing more.

Without stating the conditions, I find it a bit strange, but it is no more binding than a verbal agreement. Don't get your hopes up until all your documents have been submitted and reviewed.
Again about the property: Sometimes you talk about a ruin, sometimes about renovating. Which one is it? Those are significant differences.

I have my business account at an online bank, only the equity account is at the local bank. I found the offer there to be untrustworthy, no statement of modularities, "come by when you have auctioned the house," so just a verbal commitment of the credit line, nothing more.

Basically, you need equity for the auction. without that it won't work.

But without a commitment, it will be difficult. What will you do if you win the auction but then don't get financing?

The combination of auction & self-employment is somehow the killer.