House purchase - problems with the transaction - experiences, tips?

How could something like that be BINDINGLY recorded?

Purchase agreement with the notary; everything else can still lead to him changing his mind.

In the worst case, you end up in court with a preliminary contract.

Yes, of course, but for given reasons related to the speculation tax, he cannot enter into a purchase contract RIGHT NOW at the moment. My question is, what can I do or what and where must I record in writing that he cannot do anything more?

In what form must this be done and is it all legal? I mean, if he obviously rents the house to me, concludes a preliminary contract to circumvent the tax... won't the tax office become suspicious and intervene? Is it even possible to record all this in writing without legal consequences?

Consult a tax advisor and notary; they will most likely be able to provide you with information about tax tricks and safeguards.

He already tricked you with the 2000 euros, and you won't get that back from him either. I wouldn't do any more business with that guy.

I know, that wasn't the question

Pre-contract and 2000 euros

I have no knowledge of the legal aspects at all - but if you really still want the house, I would personally try it like this: - make a contract with the owner that sets the purchase for autumn 2019 (?). Have the contract drawn up by a notary so that it is hopefully watertight. Then also specify when you will move in - the rent payments will be deducted from the purchase price; maybe also include a clause (which is probably not valid anyway, but maybe helpful for persuasion...) that you will cover all repairs etc. And then put the seller on the spot: until the end of 2019 you are "normal" tenants. Then, when he is "allowed" to sell, a normal purchase contract will be drawn up, the old (pre-)contract will be torn up and no one will know anything about it. That would at least give you the security that if the seller goes off the rails beforehand, you can wave the pre-contract and his lost tax savings at him. Whether all this is even feasible, and desired by you and by the seller, is another matter. Have you already talked to the tenant?