Dream plot, but TAFF house - first mistake already made

Well, I would expect something more tangible instead of just "Interior finishing: €90,000" in the first offer as it stands. I don't find that signable... or is that normal? I hope to be able to argue with the price comparison: Why does the interior finishing cost €10,000 less for comparable customer X? etc.

That would already be more than some prefab house offers I know. The details of what is included in the price can be found in the corresponding construction performance description.

As already said, your "Plan 3" is certainly the smartest solution. In any case, I would try to purchase the plot separately first. This can be argued based on the fact that you really want to buy it separately due to the real estate transfer tax. Furthermore, I wonder how it should work if you were to wait 2-3 years between buying the plot and buying the house? Would the real estate agent then not sell the plot to you?? I would also ask the agent about this. The whole thing can be done in such a way that you really want to build with TAFF...

In general, you should not rush the signature on the house purchase contract. You should plan and calculate the house thoroughly and thoughtfully before you sign here. The supposed dream plot should not rush you. Your project is not supposed to become a "nightmare"...

The thing could look like this behind the scenes. Owner hires a broker because he doesn’t want to deal with the talk with the interested parties. Broker sells for a commission from the buyer. Broker also gets a commission from [Taff] if they bring a customer. What does the broker do? Connects the land with [Taff]. That way he earns twice. That’s why plan 3 or clearly tell the broker, I will buy, but without [Taff]. My gut feeling tells me, stay away from this developer. He has nothing himself. Has to find subcontractors for everything. In today’s economy, if he finds them, you end up with some wild characters on your construction site. Companies that never provide warranties because they no longer exist in 2019. Take your money and run principle. With your money. Karsten

Furthermore, I wonder how it would work if you waited 2-3 years between buying the land and buying the house? Would the realtor then not sell the land to you??

I don't think so. As I said, the realtor was the managing director of TAFF and will probably want to arrange the deal so that the house is signed for first and then the land, and with as little waiting time as possible. Pure speculation, but I can't imagine it any other way.

The matter might look like this behind the scenes.[...]

That's probably how it will be...

Regarding plan 3: The owner is over 80 and probably doesn't want to have anything to do with all the contract fuss. It will probably be difficult to convince him to conclude the contract directly with me, after all, the realtor was so kind and takes care of everything...

Would a preliminary contract possibly make sense? Could I conclude this preliminary contract personally with the owner so that the builder is then left out of the final purchase contract?

The next step would therefore be: contact the owner and clarify the situation. Then visit a notary and secure a preliminary contract (with a right of withdrawal if something is wrong with it (contaminations, land register, soil survey, and whatever else there may be, I still have to find out). If everything is correct at some point, conclude the purchase contract.

I have now contacted the owner, but he does not want to back down from the once concluded brokerage contract. Very unfortunate. So now, eyes open with the [Bauleistungsbeschreibung]...

Good idea. But is that still necessary when there are already warehouses on it? It is a former site of a (non-toxic) workshop that was still in operation until last year.

Warehouses??? Workshop???
Is it a mixed-use area? Who covers the demolition costs?
What kind of (former) workshop is this? Since when has it existed, what was there before? Which company, which trade?
There are trades where you would never guess what was dumped into the ground back then. I would especially expect a toxicological report from the seller there.

Would a preliminary contract possibly make sense? Could I personally conclude this preliminary contract with the owner so that the developer is excluded from the final purchase contract?

There is the nasty word preliminary contract

No, you have contact with the realtor who has a contract with the owner – you probably can't get out of it, because they have standard terms and conditions.