Calculation single-family house with upscale equipment

Greetings!
We (a 3-person family) are currently planning our house.
I have already created a rough drawing or model.

However, I am wondering how high I should roughly estimate the total costs per m^2.
We are planning a single-family house with 1.5 floors without a basement.
Floor area approx. 12x9.5m, white plastered -> no clinker.
Roof pitch 48°
Garage 4.5x7.5m flat roof.
Equipment photovoltaic about 6kWp
Gas condensing technology
Underfloor heating (except office/ HAR/ utility room)
Controlled residential ventilation
KFW 70
Electric shutters
Otherwise no special requirements like network, KNX or such
The rest is standard.
Kitchen is already available

We could do own work (respectively the fathers-in-law)
Gas/water installation
Roof covering
Screed laying within the family

My plan is to contract out the shell including the roof truss and windows
We will take care of the rest.

The leasehold property costs us 25k after development
and I would like to offset the leasehold interest with the photovoltaic system.

Perhaps some people in rural areas have gained experience they would like to share?

I would calculate 1800€ per sqm.
That means total costs of about 315,000€
That should include everything, such as ancillary building costs, land, etc.

Do you think that is realistic, or am I way off?

Regards
Mike

I cannot recognize the upscale finishes there, so the house can probably be built for 1,500 euros/m2. That makes 240k for an assumed 160 m2 living area. That leaves 40k for incidental costs, so at first glance, that could work.

I can't see the upscale features here, so the house can probably be built for 1,500 euros/m2. That makes 240k for an assumed 160 m2 living area. That leaves 40k for additional costs, so it could work at first glance.

Order a standard house from Town & Country, Heinz von Heiden, etc. With luck, the mentioned underfloor heating is already included. But photovoltaics, ventilation system, electric shutters, and a 4.5x7.5m garage certainly are not. The mentioned wishes already exceed >35k€ costs for the goodies budget.

You have to like ground lease. Keep in mind that these cannot be fully financed; max. 80% is usual here.

Oh... I hadn't considered the 80%.

What does that mean in detail?
Assuming:
The property costs 300,000
Loan amount 240,000???

Exactly. The loan amount is not limited by the bank, but because the [Erbpachtgeber] wants it that way. So ask them about the lending limit. 80% is common, but deviations in both directions are not excluded.

Assuming the cabin really costs us 315,000€

80% of that is 252,000€

So we would have to bring 63K€ of equity?

Am I seeing this correctly?