well, remembers correctly as always ;-)
We (my brother and I) built 2 semi-detached houses with 2 residential units each (so 4 apartments) on TWO plots of land together. In total, we have 5 parking spaces and still plenty of garden. The plots together are about 640m² large (small) and approximately 300m² of living space was realized. Upper floors each accessed via external stairs, technical equipment outsourced to an external technical room located at the boundary.
Affordable? I think so, but some might see it differently. In hindsight, of course, definitely affordable with under 1% interest and lots of gifted money (KfW etc.) The whole thing in Münsterland (NRW) and in compliance with the corresponding state building code (one parking space per residential unit...)
The very detailed thread about it has unfortunately been deleted.