Single-family house approx. 155 sqm + separate living unit 40 sqm. First draft. Any suggestions for improvement?

In this location, according to several rent index sources and realtor information, it would be about 11-12€/sqm, so about 400€ cold rental income + possibly a carport space and a return of about 5%.

Great, then after about 20 years you would have recovered the costs. The only problem is that you constantly have to renovate with students, and after 20 years you can practically gut the place.

What bothers me is the garden access or lack thereof. The rooftop terrace is nice for eating, coffee. And the kids? Sandbox, slide, etc. Always having to go across the house for a glass of juice? Parents are always sitting there and can do nothing, not even dinner.

How did you calculate the 5% return? The money for building the [Einliegerwohnung] still has to be raised first. Taxes also apply plus maintenance.

How did you calculate the 5% return? The money for building the granny flat also has to be raised first. Taxes are also due plus maintenance.

That is correct. Already entered in the future household budget. Reserves for maintenance + rent losses + insurance etc.

Great, then you would have recouped the costs after about 20 years. The only problem is that you constantly have to renovate with students, and after 20 years you can practically gut the place.

What do you think of the proposed solution:
Building reserves for maintenance + loss of rent + withholding deposit in case of emergency + used but good equipment, bought on eBay Classifieds for the rented granny flat + own effort (here and there).

During my studies, we even lived with 3 students in a UG shared apartment (3 rooms, 1 bathroom, 1 kitchen) in a family house with a detached house.

Then you know what your family can look forward to

Due to a separate entrance to the granny flat and the main living area, contact with the landlord (despite 2 children) was barely noticeable for all of us.

But here it is very noticeable: on the one hand, you drive your cars to his garage entrance, to then?... walk past the apartment to go around the house to get inside or go through the storage basement. Which is nicer? I find it totally thoughtless. Who wants to enter their house through a storage room / utility room, stumbling over some placed play or sports equipment. And then possibly eavesdrop curiously through the connecting door to the granny flat?!
Or else go around half the property?
Contact points on the ground floor to the garden only exist via the front door. You don’t need to build for that. That would be inadequate for me.
Considering that the ground floor and upper floor are already very large, the staircase is quite modest, which is not negative. I find the living-dining area too large... uncomfortable. Too far from the kitchen.
At the moment, I can’t really judge whether these large rooms have something positive/generous or are simply inflated. I don’t want to always criticize something like this, but for me, a portion of generosity in the house requires, in addition to large rooms, some highlights like an open staircase, atrium space or an open gable. If these aren’t present as here, then I would rather plan the rooms to be “normal size.”

For me, definitely the big flaw in the house is the missing contact point of people to the garden, but instead the focal point is the granny flat for the family.