Everything beyond that is comfort.
Yes, a house with a granny flat is simply comfort. And if you equip 150 sqm, which is not unreasonable in size, with an additional appealing apartment, then that corresponds to the living comfort.
I don't think you as a landlord benefit from adding a dead-end living space.
We have people in the immediate vicinity who have consciously downsized in old age. The ground floor apartments there are all 35-50 sqm.
What interests me here: have you now inspected all possible houses with granny flats? Or do you just want to believe what you've been told?
Does anyone of you live with a NW orientation?
My next house would have at least a NW terrace. But that doesn't mean you want it too. And it doesn't mean that we are dissatisfied with our current orientation.
It's all a symbiosis of the possibilities you have.
Also, the discussion about switching kitchen and living room: that is very close to the old design to change it that way. But there are also enough houses whose terraces have a complete north orientation—and this orientation also has its justified place because it clearly has other advantages.
It is just as dark until 4 p.m. In winter, the sun sometimes never reaches there.
It doesn't have to. You live in an apartment? Do you often just hang out on the sofa and enjoy the sun there?
If you have a garden, you do quite different things in good weather than sitting on the sofa and looking outside.
We have a north-facing bathroom. It is bright enough because it has a window, and in summer the sun rises in the NE and sets in the NW, so when we use it, there is still sunlight through the north window.
I'll link a post of mine from elsewhere
By now, everyone has shading on their south terrace.
One also has to say repeatedly that south terraces don’t have sun in the evening.
Terraces are not meant for basking in the sun in your own garden like on vacation. 1. For that, people like to have their lawn or a spot in another corner of the garden. 2. In everyday life, one often doesn’t want the sun because it simply interferes with daily work.
When planning, I like to separate window and terrace use: windows preferably in the south to get light and warmth into the house from October to Easter, terraces preferably in the west or north to catch sun rays there in the evenings during summer everyday life.
Everyone has to look for themselves how they design their daily routine and day.
If you often plan coffee visits from grandparents, you should have a terrace that is somewhat shaded. Those who have free time during the day and like to sunbathe have their deckchair somewhere else than the dining area for barbecuing.
If I had to build again, I would plan a small south terrace but focus more on west/northwest.
West again has the disadvantage of wind, but you can counter that with planting and elements. I also don’t know anyone who hasn’t planted their terrace at the single-family house to make it cozier.
Furthermore, the entire apartment faces the street. The view of greenery is limited. With this arrangement, I see more disadvantages than advantages, even if the layout of the granny flat is clearly nicer.
Well, you can plant greenery yourself. That's your own responsibility. The same applies to neighbors; you take care of green border plantings, hedges, and such to avoid disturbing each other at the other's driveway.
What disadvantages do you see? Normally, instead of a granny flat, half of the rooms face the street side. I think you entangle yourself too often with the argumentation.
About the slope, I can say little: sometimes it seems a basement is reasonable, then again not. 1.20 m is no reason for a basement.
I hope the OP doesn't immediately complain first thing that he doesn't like a crippled hip roof
I also got a little shock. However, I find the approach with the granny flat location interesting, but personally, I would probably be a bit too stingy with the plot there.