Of course, the child allowance is counted as income. Why not, it is a fixed and sustainable income. It is not calculated whether a child can be supported by it, but whether the household calculation of the respective bank adds up.
Above all, it is so unimportant given the TE's starting position.
It remains to be examined to what extent an employer loan is possible, whether the previously low equity capital is in a building savings contract, and if a small unsecured loan is possible, which would increase the equity capital – even if externally financed – whether the state funding from LaBo is an option, and whether personal contribution can be made.
I do think that financing can be represented at a certain level in terms of amount; if necessary, a subordinated loan – even if more expensive than the mortgage loan – can also be used to "catch up" on the missing equity capital.
All in all, the thought process or the project should be pursued further and a suitable and feasible financing concept developed, as well as the construction costs calculated precisely.
I give my thumbs up here.