Demolition, Real division, Semi-detached house

When purchasing, have the plot subdivided and provide for a corresponding building easement. Then everything would possibly be part of the contract and handled through the notary. (If applicable, a demolition permit might be required anyway.) This may also ensure that a semi-detached house is eligible for a building permit, otherwise the building easement would not exist.

I doubt that the mutual cultivation obligation of the owners of the new half-plots implies that the municipality would then have to allow semi-detached housing; I see lateral building zones emerging on the divided plot, from which one cannot simply release each other. Dividing a still contiguous built-up plot could already be challenging, it would at least not be an ordinary case.

A building encumbrance is an acquired right. Especially nowadays, densification of building space is a major topic. At least politically, because without adjustments to parking space regulations,... this doesn't bring much, at least in urban areas. Otherwise, there is no need to speculate even in lay forums when a notary is available for such questions. A repurchase right could even be provided in case no corresponding building encumbrances are possible. As a rule, the authorities work together, i.e., the building authority will possibly provide an internal statement on the building encumbrances anyway.