House on a slope with 2 granny flats

The private garden is planned on top of the garages, which apparently was not quite clear from the plans.

It even clearly looks like a completely wooden deck terrace, zero greenery, so nothing I would call a garden.

You are already a big family – do you really want two other families around you?

Tenants who yell down from the rooftop terrace to the parking space with their Schantalle – a dream.

Currently, a building inquiry is underway in which I have specifically asked this question. Two houses down the street, there is a multifamily house with 10 residential units, but the development plan currently only allows for 2 residential units. So it is quite possible that we may not be able to build as planned. Then the attic apartment would probably be omitted. However, in our opinion, the property clearly calls for an upper granny flat, since there is a separate driveway and access upstairs.

Are you allowed to build a multifamily house in your residential area? For example, here only single-family houses with one granny flat are permitted for 3 residential units

I already wrote above that it’s because of the program. It doesn’t seem to have been designed for planning outdoor areas. Maybe it’s also because of me, I’m just an amateur. The garden should be paved with natural stone or wood in the back area, but in the front part—over the garages—it should be landscaped with lawn and bushes.

The thing with Schantalle is exaggerated, but definitely an argument. We really have to think about it.

It clearly looks like a terrace completely paved with wood, zero greenery, so nothing I would call a garden.

Tenants yelling with their Schantalle from the roof terrace down to the parking space—a dream.

I don't think the property screams for a granny flat. Especially with 4 children, the garden is quickly put to use
Swing
Sandbox
Paddling pool for the little ones
Water channel
Slide
Open space for ball games
Trampoline
Balancing beam

I think the apartments ruin a lot.

Do I understand the model correctly? You bought a very expensive plot of land and the financing model now consists of building additional residential units and renting them out? In my opinion, it only makes sense with a high volume (many units) and a long, long term. The rent-to-purchase-price ratio (and thus also the rent-to-production-cost ratio) is especially poor in particularly high-priced areas, i.e. rent is 'relatively' cheap. Are the garages located at the property boundary? It looks like it. This normally means the use as a terrace/garden would not be approved. I think more brainpower will have to be invested in the project, but wait first and see what the building pre-application says. If two residential units are allowed, they won’t approve three.

The thing with Schantalle is exaggerated, but definitely an argument. We really have to think about it.

And if it didn't have three corners, then it wouldn't be my hat

In my opinion, it only pays off with high volume (many units) and a very, very long time horizon. The rent-to-purchase-price ratio (and thus also the rent-to-construction-cost ratio) is particularly poor in especially expensive areas, meaning rent is 'relatively' cheap.
Are the garages located on the property boundary? Looks like it. That would normally mean use as a terrace/garden is not likely to be approved.

Even building second residential units would not be subsidized if it paid off on its own. Renting out two residential units is "thought of" as a zero-sum game during the active working life of the homeowner and afterwards to supplement retirement income — from an investment perspective, more of a lame duck. One should preferably build living space for personal use, not with the perspective of a small-time dealer.