Be reassured, no house provider ties up capital to buy a plot of land away from you. The story goes something like this: 0. prospects hardly respond to simple advertisements, so you wait for them where they will appear on their own (he has to come through this narrow alley...) – so you "advertise" in the form of supposed "plot of land ads". 1. someone offers a plot of land; 2. a salesperson contacts this seller and wrangles permission to offer the plot to their house prospects – this costs the seller nothing, so they usually accept without resistance. 3. now you check what the development plan allows there – result, for example, house model 135. 4. the house provider then runs a house sale ad, "Model 135 from EUR 348,000 (construction start very soon) near 86420 Grundstücksdorf, more details about the location on request". At no point were they a binding sole agent, nor would they have ever owned the plot of land. You have to calculate the plot price on top and, of course, negotiate with the landowner. You will never find out who that actually was if they have meanwhile sold their plot. Then they look for substitute plots for you, of which the Easter Bunny could tell his grandma that they are equivalent to the plot used for the supposedly concrete offer. If I were king of Germany, lightning would strike such short sellers while they are shitting.
There are already threads about this here, maybe @11ant can help further
He last did so here: – there is a small bag of links.