Child benefit for building and other subsidies?

"From the debate" --> who exactly says that?
I am neither talking about the Euro rescue nor Hartz 4, but exclusively about the Baukindergeld. The nonsense of one is not canceled out by the alleged worse of the other – this must be discussed separately.
400 million is also not per year but the estimated cost for the specific year 2018. Until the year 2027 (or hopefully not that long if it is abolished before then), the amount will increase annually simply because new funding cohorts will be added (and in later years, when not only catch-up effects like with all of us exist, but 2 or 3 people actually make their decision dependent on it, more than this year). The annual amount is then estimated to be up to 22 billion. So your argument is the one that is refuted.

I partly agree with Kekse; the subsidy will cost the taxpayer more than 400 million and the predicted 4 billion funding maximum will probably also be exceeded. However, I cannot imagine 22 billion annually for the life of me because:

1. Unlike the homeownership grant, we exclude a large part of the population. Without children, you simply get nothing.
2. Now only private building projects that are actually self-occupied are supported. Both were not the case with the homeownership grant.
3. The subsidy today for 2 children corresponds roughly to the amount of the homeownership grant that was paid out 15 years ago. Only today the single-family homes are twice as expensive. Yes, interest rates have fallen, but the installment also seems to have decreased. In other words, people simply pay much higher sums for a much longer time, so the total costs also rise. Despite Baukindergeld, fewer people can afford this today than 15 years ago.

But as I said, everyone has their opinion. I look forward to getting 40k€ when the time comes, and if not, then I’ll sulk for a day and then that’s it.

The 22 billion was stated in Handelsblatt, but summed over 10 years.

Whether you sum up a funding cohort over the entire funding period (i.e., over 10 years) or sum up all 10 concurrently running funding cohorts, it makes no difference—at least as long as the same number of applications are submitted every year. If the same number of applications are submitted each year as in 2018, this funding is completely pointless, because it then makes no difference to anything but is only taken advantage of by people like you and me who would have built or bought anyway (I simply assert that almost everyone who starts building this year would have done so regardless). In that case, the Baukindergeld (child-building subsidy) costs an estimated 4 billion per year after full implementation (cost estimate by the initiating government for this year times 10 concurrently running funding cohorts). However, if it does show a significant effect, it will also become significantly more expensive. Will it actually be 22 billion? Possibly not. That would mean that more than 80% of the recipients would NOT have bought/acquired anyway. But even with a conservative estimate, it will probably amount to annual total costs between 5 and 10 billion. And I would know a bunch of things you could do better with this money than pay for you and me to have a terrace (and indirectly some construction companies their new car).

I have a question for understanding.

We signed the house contract last month, the construction begins in autumn/winter, move-in spring 2019.
At the moment we are childless, but are planning the first child next year.

Do we then have the right to [Baukindergeld] (for 9 years)?

The exact conditions are still unclear, but according to the parliamentary group agreement, probably not, the first child must already be born at the time of the building permit.

Yes, that is the current trend. The opposition has already criticized this because it practically dictates life planning. Perhaps something will still change, the concrete funding guidelines are yet to be awaited.