Hello ypg,
DH can serve as a basis for discussion.
A two-family house with a "staircase" is not desired.
A single-family house would probably be accepted.
Furthermore, due to the long, narrow plot (20m width) and the sloping location, only very narrow, elongated semi-detached houses would result. Boundary construction, e.g. for a carport or parking space, is also not so easily possible (thanks to the steep embankment in the upper part of the plot, the 3m limit is quickly exceeded).
To be honest with myself, it is a great plot for an upscale single-family house with an unobstructable view in a quiet location and a 15-minute drive to the big city. However, in my opinion, such a property is rather difficult as a rental object.
At the moment, I am slowly really considering placing a nice, modern holiday home (preliminary as Flying Spaces from Schwörerhaus) on it and simply using it within the family. It does not really help as an investment or retirement provision, but at least you have something for yourself.