Link property purchase to future buildability?

And after all, it is the seller who acts as if the stamp is just a formality and his desired procedure can certainly be implemented. Then he should also confidently guarantee that – but as I said, that's yesterday's news, it was a castle in the air.

I have (so far) not backed down from the property, only from the specific house provider. I will open a separate topic about the property if that is okay, to get some more precise assessments about what I would be getting involved in here.

On the other hand (the buyer is supposed to pay first and then hope that the development can actually be realized as promised by the seller), it is equally not "fair," is it?

Promising a characteristic of the property, although it is not officially guaranteed, is not a nice thing to do either, you are right. I had not understood it that way and I would not make an offer like that to anyone. If you were to receive a guarantee - how would the payment or avoidance of incidental purchase costs be arranged?

If you were to receive a guarantee - how is the payment or avoidance of ancillary purchase costs then regulated?

That's what I'm wondering too - I fear there really can't be a practical solution:
A) the purchase (land register) is kept pending until the building application is approved -> the seller probably won't agree to that or I wouldn't want a strict deadline by which the planning has to be rushed through
B) the seller grants an option to reverse the purchase - the notary/tax office will certainly want their share twice