Financing a single-family house with land subdivision - risk or opportunity?

Yes. Ratio 55:45 (partner: me)

I didn't mean the income but the tax class. If currently both have IV, it could be switched to III/V, which would somewhat compensate for the lost income.

I did not mean the income but the tax class

Since (still) not married, both 1

offer them the other half of the ground right away

Thanks for the tip, that’s how we planned it. However, for a different reason, namely that the property can be sold as a project and is therefore more attractive. All other tips naturally also support this

Legally build a two-family house, but divide it vertically

I will definitely include that again in the list of questions, we also discussed it once with our advisor but somehow, at some point, it was off the table again ops:

I have attached here another example of a double single-family house development (with two alternatives for a double garage). Of course, the sketch is only for orientation.

What exactly is meant by this statement? With a semi-detached house, I also can't directly access the street

That is correct. We are in the second row, so our property starts directly with our semi-detached house, meaning we don't have the strip at the front (or don't have to).
Since you are directly on the street, it's of course different.

I have attached what I could imagine for a semi-detached house. I tried to divide the property equally and angle it 90° from the street.
This way, both parties would have a bit more green space "in the back".

If the garage is 6x6 meters, then the strip between the houses is 5 meters wide? From the ground floor window, you only see a wall or the neighbor's living space. Sitting on the terrace is also very uncomfortable with a wall. And then the garage in between. The green square in the very center is enclosed on three sides. You can only use that as a garbage collection point. You don't seriously want to build like that, do you?

Plain language: Push the two houses together and make two semi-detached houses. Everything else is unreasonable. With a semi-detached house, you have more privacy than like this.

If the semi-detached house were divided as a WEG (i.e., formally a two-family house), a combined garage would also be an option (I assume the slope goes down towards the street ... If the plan is oriented to north, then both houses would also have a south-facing garden/terrace.

If the semi-detached house were divided as a condominium (i.e., formally a two-family house), a combined garage would also be an option (I assume the slope goes down towards the street ... If the plan is oriented north, then both houses would also have a south-facing garden/terrace. [ATTACH alt="Bild2.png"]51351[/ATTACH]

But then it would be quite dark on the ground floor of House 1.