Financing project single-family house in Central Hesse

I am talking about the house. It costs 20k more if [Kfw]. Additionally, I personally find 10 and 15 years too short. But just like the statement about the 20k more because of [KfW], this is also a personal opinion.

With KfW 124, there is no fixed interest rate period longer than 10 years.....

Where I come from, houses of the size described by the OP are built at least to KfW55 standard, turnkey, without a basement for 300,000 EUR (of course solid construction). So I still don't understand why you are estimating 60,000 EUR more.

Then go ahead and build your 160sqm house for 300k. Here, the calculation is currently about 2000 per sqm. = 320k + floors, ceiling, walls = 340k + exterior facilities and buffer = 360k Satisfied? I just wanted to express my opinion. You obviously have a different one. Where I come from, I recommend calculating with more rather than having to finance expensive additional costs later.

Then go ahead and build your 160 sqm house for 300k. Here, the calculation is currently about 2000 per sqm. = 320k + floors, ceiling, walls = 340k + outdoor facilities and buffer = 360k Satisfied? I just wanted to express my opinion. You obviously have a different one. Where I come from, I simply recommend calculating higher rather than having to finance additional costs later.

That's what I meant too. The house seems rather in the affordable segment to me. Additional financing is always more expensive. Especially with Naspa.

what speaks against the KfW 153 program in combination with 124? Lower interest rate than at the house bank and 15,000 EUR repayment grant, or is there a catch related to the original poster?

That the 15,000 grant requires a KfW 40 plus house? And this additional effort usually exceeds the grant in most cases.

And yes, 2.02 would be cheaper than 2.06; but that rate is only for 10 years.
I don’t really see an advantage there.

The ancillary construction costs could be too low if connections, a soil survey, and surveying have to be paid for with them. At this point, I would not advise, but calculate; all the costs can be determined. In your place, I would always let the general contractor handle construction electricity and construction water, as well as all earthworks and earth removal on a lump sum basis. The house price might be accurate, but maybe you should get offers first. In Lower Saxony, we paid about 1800 euros per sqm for our 200 sqm house with good fittings, including painting work.