Floor plan 4-room rental apartment - Rentable?

10m2 as a children's room is too small in my opinion. Without measurements it's hard to judge, but you can hardly get around the bed in the parents' bedroom, right?

well, as a mother of two, I would only move in there if I had no other choice. The size of the children's rooms wouldn't even be the problem, but as a family, I want to have my washing machine upstairs, there's no storage room, and with children, I urgently need one. I don't want to have to lug the next pack of diapers down to the basement. Better make it a spacious three-room apartment. A young family fits perfectly in there and still has room for the soon-to-arrive baby.

: beautiful kitty! Norwegian?

Thank you Maine Coon

So, I am trying to shed some light on my question:

Floor area ratio: 0.4. Site coverage ratio: 0.25. That would result in a total of 217 sqm according to the calculation before 1970.

The property is located in a village of 700 inhabitants in the hinterland of ÜB, Lake Constance, 12 km away. Quiet location, wonderful view over the valley. South-facing slope.
The neighboring plots are built with single-family houses, most plots have over 800 sqm.
After a preliminary discussion with the mayor and the local building inspector, we were given the impression that rental apartments are very welcome, but not in the actually maximum allowed size. The house should fit in better with the existing development. Neighborhood disputes should be avoided. Therefore, the restriction to 15 meters width, with a depth of up to 13 meters.
Parking spaces are required as follows: 1 space for apartments under 60 sqm, 1.5 spaces for those over 60 sqm. This was an oral statement that cannot be found as such in the parking regulation and therefore needs to be clarified.
Infrastructure. In the village, there is a church, an inn, a new community center in which events regularly take place – for young and old. Overall, an active club life. There is also a kindergarten in the village. The primary school is in the neighboring village, 3 km away. There are also numerous shopping options, doctors, pharmacy. Secondary schools are then in ÜB. Bus connection is not perfect but still sufficient.

With assumed construction costs of €2200/sqm, we would have to achieve a rent of at least €8.80 to make the whole project worthwhile. The rent index currently shows a cold rent between €8.3 and €10 per sqm.

And now to our considerations.
Construction of a semi-detached house with 2 small apartments in the basement, with ground-level access to outside. This would result in nicer, larger apartments for families, but it does not pay off for us.
Therefore the desire for 6 apartments, which are, of course, smaller and more suitable for older couples. Hence my first floor plan draft. When occupied by a couple, it is probably not so bad if two rooms lead off the living area, but with children it is. The room sizes are not generous either, but also not unusual for rental apartments. We have lived for a long time with 3 children in a similar situation.

Access via an external staircase is something we have realized similarly in a rental house of my in-laws. It works well and so far no tenant has complained about it. I rather see an advantage if everyone has their own entrance. Storage options are not strictly required – at least, I have not read about such a regulation anywhere. Possibly boxes as a substitute for a cellar could be installed under the parking spaces if the cellar will not be accessible to everyone.

So, now it’s your turn again. I hope I have not forgotten anything. As said, it is not about this exact floor plan – it was only a thought experiment to visualize the possibility.
Looking forward to further input.

In case I have forgotten something important.

Especially if it's not (only) about this floor plan for you, the other floors and the property are part of it. How else should one be able to judge it?

By the way, I find (own) external entrances good, I'm not really a fan of stairwell small talk. But then I really need to have enough storage space in the apartment, as someone already said, so that you don't have to go outside to get to the (laundry) cellar.

Especially if it is not (only) about this floor plan, the other floors and the property are included. How else should one be able to judge it?

I agree completely