Brokerage Contract Agricultural Land

Well, but that wasn’t the question here nor is it our problem. If it’s somehow land expected for development and located in a sought-after area in BW, someone stupid will be found.

I was recently in exactly this situation as a buyer:
* Purchase of farmland
* Seller had exclusively commissioned an agent (whom I never contacted)
* Seller believed that it would eventually become building land (and had corresponding price expectations)

The purchase contract has now been completed, the solution was
* the agent did not receive any commission (nor demanded any!), as he had nothing to do with this mediation (of course, I do not know the agent contract)
* the purchase was concluded at the price of farmland (without any surcharge). The contract contains a clause according to which the seller will receive a (high) additional payment if I use the property as building land within the next ten years (i.e., build on or sell it)

Well, but that was neither the question here nor is it our problem.
If it is somehow land earmarked for development and is located in a sought-after area in BW somewhere promising, a fool will be found.

Amen!
If you knew what has already been sold by developers in the Stuttgart metropolitan area and then became building land two months later, you would talk about it differently.

If you knew what has already been sold by developers in the Stuttgart commuter belt and then became building land two months later, you would talk about it differently.

Wow, in Stuttgart does farmland become building land in two months? Elsewhere, that takes years (changing the land use plan, preparing the development plan, passing statutory resolutions, involving authorities/offices/official stakeholders, etc.).

If you knew what is really necessary to convert actual farmland into building land, you would talk about it differently. Even in the Stuttgart commuter belt, rules must be followed – and they don’t take just two months.

Alone the preparation of a new development plan should take between two and three years. Just for your information.

was was sold to a property developer

You are naming the crucial point yourself directly. With your 1000m2 as a private person, there’s no chance of getting building land within 2 months ;) Rest see my predecessor :)

Wenn das irgendwie Bauerwartungsland ist

That should be evident from the land use plan. You can just look it up. But the OP writes "field". And who will then bear the costs for conversion into building land + development costs is still up in the air. That adds up to a few bucks...