Child Building Allowance / Homeownership Grant - Move-in Date Dilemma

Application is possible from the time of taking up residence, this is the official rule.
So someone would actually have to move in for it to be compliant with the rules, right?

And why can't at least one of you move in there already with just a sleeping bag and suitcase?

Morning,
exactly, who says you have to live there with a thousand pieces of furniture.
Shift your main residence there now (as your primary residence) and register accordingly, and keep your old apartment as a secondary residence for the time being.
With the appropriate subsidy, I would calmly go through the effort of registering and deregistering, etc., it can even have tax advantages if it’s somehow work-related.
Regards, Olli

The neighbors can see that you don't live there

And besides, I hardly believe anyone here is asking the neighbors. You could also have first gone on vacation after all the buying stress... Olli

I would inquire about what needs to be done to officially relocate the [Lebensmittelpunkt] there and then initiate the process. I would neither want to cheat nor waive the money. One can conclude it with a clear conscience; and for such an amount of money, the effort is worth it.

well, such a purchase came suddenly and unexpectedly. I'm not a fan of cashing in on subsidies when it could have been arranged beforehand

And how do you arrange it beforehand if no free objects are available?
Just re-register and that's that.