Single-family house - approx. 150 sqm - without basement - Who has ideas? Thanks

To be on the safe side, the neighboring owner wants an entry in the land register; for the building authority, his written confirmation is sufficient (if I want to build in the rear area of the property), he had the same with his neighbor, everything is fine.

The old building was a residential building (built in 1900), although the area is commercial, 80% are residential buildings, about 15 residential houses.

The architect calculates the project at about 420k (including the plot) - without own contributions. The bank gave the green light, but I could get more if necessary (about 30k).

Admittedly, I am a knowledgeable layman, but someone like will certainly be able to provide more professionally grounded information

The question is what the plot costs.

The question is what the plot of land costs.
180 m2 is roughly 360 K€ by rough estimation. In addition, the incidental construction costs (especially partly high connection fees or construction cost subsidies that need to be paid). Also the plot, all work outside the house, plus carport or garage, outdoor surfaces, etc. etc.
Then also what is usually added during the upgrade (floor coverings, etc.).
Roughly: house 360, plot x, upgrade 20, incidental construction costs from 30, landscaping (fences, surfaces, lawn, etc.) at least 20.
Without the plot, I am already at at least 430 K€, note without kitchen. If plot less than 70 K€, that’s certainly 500 K€ in total…..
And depending on soil conditions, it can definitely become even more.

please stop beating this topic to death .....

this is about the .......that was my concern.

The echo chamber you're looking for is one door down.
Good luck, I'm out.