Time of contract signing for house construction

The contractor wants us to sign the contract this year so that he can plan better, t

The legal situation changes to the disadvantage of the general contractor as of 1/1/18, so the interest is currently particularly high.

What have you done now? I have a similar case. Costs were supposed to increase by 3.5%, which also made me a bit uneasy. Then he offered to write into the construction contract that the contract only comes into effect if I bring a financing commitment within 6 months. If I don’t do that, no contract will be concluded.

A proper construction company already had the changes from 2018 as standard in 2017.

We have signed the contract. It includes a free right of withdrawal subject to property purchase and financing.

I must add, however, that we have already expressed our intention to purchase to the seller for the property purchase. We are just waiting for the documents from the notary.
And we have already received financing commitments from 3 banks.

The only problem left is when the building readiness in the newly developed building area will be established...