Is the financing plan realistic?

We had no buffer - risky, but also possible.

Yes, we had one - the photovoltaic system. That is now gone too

We were probably a bit cautious there, but better than the other way around.

Good that I get to read such a statement from a builder! I wish many more builders would act so realistically

Rhenish greetings

With prices, it is unfortunately becoming more and more difficult – definitely reasonable, although I would never really finance a buffer (which is also done), but would always take it from equity.

A new car after construction would certainly be great

In the shell construction phase, I also thought that the buffer (from equity) was unnecessary, as we saved money in many places there. However, we compensated for the savings during the interior finishing (here some different tiles, there some additional tools, here a new wall unit, etc.), so in the end we had calculated exactly right. We didn't have to touch the buffer, but it allowed us to sleep better.

Part of the buffer will go into the design of the outdoor area in spring (there will be the expensive paving) and the rest will continue to serve as a buffer. Possibly, more will be put into special repayments in the coming years.

whereas I would never really finance a buffer (which is also done), but would always take it from equity.

You are going in circles, I think. Somehow I tried to make that clear with my calculation above. If you need 500,000 euros and want a 10% buffer, you need 550,000 euros (YMMV). From that, you subtract your equity and get the external capital requirement X (which you then relate to the production costs according to the bank in a second step to see the loan-to-value). Now you have three options: 1.) take out a loan for X euros, 2.) increase equity by 50,000 euros (inheritance? lottery?) or 3.) scale back.

And where am I going in circles now? Your example is nice, but there are other constellations as well.

What about the one who wants to borrow 400,000, has 30,000 equity, but wants 30,000 as a buffer (which seems to be little here in the forum)? Going into the calculation with zero equity is rather bad – so I set the acquisition costs higher and hope that I don't exceed the lending limits with that. Depending on the area & creditworthiness, that can then work.