Contract clause for subsequent purchase price adjustment in the new development area

Has anyone of you ever encountered something like this or does any of you have experience with the legal situation?

Daily practice in commercial developments. Higher land use than expected = extra cost. In case of resale after development with higher purchase price = extra cost. already wrote it: usual improvement certificate - although very rare in private cases.

The notary is a lawyer.

No. A fully qualified lawyer, yes, but only in some federal states are there lawyer-notaries at all. There are also federal states with only official notaries.

But in this case, he still acts in the interest of the investor

No, never. A lawyer-notary cannot act as a notary if he has already acted as a lawyer in the same matter.

I would unfortunately not speak of profiting here.

Yes: if the improvement occurs, it increases the value of the asset – and the seller would get nothing of it without the improvement certificate, just because he sells you the property now rather than later.

Higher land use than expected = higher price.

Exactly, that could also happen: garden land has no floor space ratio at all, but after the noble assessment for building land, it can have a higher floor space ratio than, for example, the nearest existing building areas, on which the presumed value was based. You (@ TE) see, such a silly meadow can be a high-performance investment.

I find that somehow intense. But does the investor still exist in 10-15 years :) no plaintiff no judge.

What extra price are we talking about if the garden plot would now become building land?

Is it 10-20 or 567k?

Similar clauses are also common, for example, when purchasing arable land: "As soon as a valid development plan comes into effect for the area, an additional payment of XX euros (alternatively: XX %) is due." This is how I would interpret it for you now as well. But I don't see any problem with that, because your "garden land" would then be worth much more as "building land." If you do not want/cannot pay the money, you always have the option to sell only the "garden land" (possibly significantly above BRW). If the "garden land" is now only an addition to the property and not absolutely necessary, then I would buy! I would then design the garden in such a way that this is always possible.

No. Fully qualified lawyer yes, but only in some federal states are there legal notaries who are also lawyers. There are also federal states with only official notaries. No, never. A legal notary cannot act as a notary if he has already acted as a lawyer in the same matter.

Then just call him a lawyer and not a lawyer (colloquial), but both are lawyers. The difference is that a lawyer acts in a partisan manner and a notary acts impartially. Either way, the notary is paid by him and is responsible for exactly such problems and must provide advice; that is what he gets his princely fee for. And that should also be the first step: go to the notary and have it explained.

I would not agree to assign 100% of the value increase to him, after all, you have costs and risks. A negotiation goal could be to regulate the share. And, if realistic, to make the clause effective only when the new building land is also sold. Otherwise, you may have a liquidity problem if the investor wants to assert his claim in 20 years.