Semi-detached house for capital investment. Sole investor or with brother?

Hello dear community,

I would like to gather some opinions and suggestions regarding a planned project. I want to have a semi-detached house built purely for renting as a capital investment, whereby my brother wants to move into one of the halves (not permanently). The question is whether I should run the entire project on my own and act as a landlord for my brother: if I comply with the 66% rental rule, I can also deduct a lot of work and expenses for this. Alternatively, we are considering sharing the semi-detached house and each getting half. My father also suggested that he take over the land and my brother and I the semi-detached house because I/we could get better loan conditions that way? Although I think there are then too many players involved in this small project.
Here are some key data:

about me:
Gross annual income €50,000 with a permanent employment contract.
No current loans and no property owned.
Building savings contract with €10,000, as well as about €25,000 equity.
No wife, children, etc.

my brother:
Gross annual income €36,000 with a permanent employment contract.
No current loans and no property owned.
Building savings contract with €5,000, as well as about €10,000 equity.
No wife, children, etc.

my father:
Gross annual income €50,000 with a permanent employment contract.
Owner-occupied house, rented semi-detached house since 2014.
The rented semi-detached house is registered as a land charge on the family home.

The semi-detached house will be built in a new housing development; I estimate rental income of €700.00 /month cold rent excluding additional costs per unit (for my brother then somewhat less). As a comparison, I took my parents’ semi-detached house, where a new rental contract was signed just last month. The living area will be roughly the same.

A plot of land has already been promised to me: 650 sqm for €68,000. I have an appointment at the real estate bank this week, where I will certainly receive a first financing offer; I have already submitted my documents and proofs there.

Thank you very much in advance for your help, suggestions, and opinions.

Hello, with your income and equity, please forget it. Much too high risk, since strangers are moving into a new house. Your brother is only living there temporarily.

Better go for owner-occupied property first.

Why am I building new just to give it away??

With 50k gross you can't finance a duplex. Roughly estimated, let's calculate 2x130m² without a basement at 1800/m² each. You already have about ~470k pure construction costs. Then there is the land, the incidental purchase costs, and the additional construction costs. We are certainly talking about at least 600k total costs. Your equity may just cover the incidental purchase costs, your salary might allow for a monthly installment of 1000€. But the installment for your financing requirement of over 550k is rather around 2500€, how is that supposed to work?

I would be interested to know what you intend to achieve with this? I don't see any profit from rental income there.

I was thinking more along the lines of 90-100 sqm. That is also the size of my parents' semi-detached house. I would pay off the installments through the rental income after the completion of the semi-detached house.

In the long term, I want to provide for old age in this way.

I was thinking more of 90-100 sqm. That is also the size of my parents' semi-detached house. I would pay off the installments through the rental income after the completion of the semi-detached house.

In the long term, I want to provide for old age through this.

Forget it, no bank will finance you like that.