How do I go about house planning?

Hello. We would like to build a new house and apply for a plot, but we don't know how to plan in order to also present a realistic calculation to the bank. We are from Bavaria and have read that the prices here are calculated higher. How did you do it? First ask companies for turnkey offers? What I should also add, in the entire building area only FD Max 5 degrees are allowed, so a monopitch roof. I keep reading that you should reckon with about 2500.- per m2. Is that including a basement? And what do we have to expect for a double garage? Does anyone from the area have experience with the prices or can name companies that can help me plan properly? Have a nice evening

Where exactly is the "area"? The district Bad Kissingen, for example, has quite different prices than Starnberg. Is the plot firmly promised or already bought? An FD with 5° can also be called a monopitch roof, it just needs a watertight underroof, but the water can still drain off. And so the monopitch roof is actually the cheapest roof type of all. As opposed to a true flat roof by the way, which is rather an expensive roof type. Thanks for your answer. We would build in Neutraubling m2 400€. Plots are now being sold which we would apply for with about 550m2. Currently we have a semi-detached house (just around the corner) which we would then sell. Best regards Bettina

No, a cube/flat roof often has this pitch. Still, it is called a flat roof. But whatever. Even flat roofs are nowadays no longer the cost factor.

I assume you have already tested your limit with the bank?
I would approach a nearby builder and ask him how much a cube with 160 sqm according to the Energy Saving Ordinance would cost. Heinz von Heiden, Schwörerhaus, they all have the model house in cube form. Please plan at least 50,000 more for equipment. Then painting work and flooring with 20,000. Additional construction costs with at least 30,000. Better to assume 50,000. It could be rocky ground. A soil survey would of course be great to have done before purchase.
So, you need: land and incidental purchase costs
House e.g. 150 sqm x 2200 = 330,000
50,000 said equipment
50,000 additional construction costs
20,000 floors etc.
25,000 garage and co
25,000 outdoor facilities
15,000 kitchen
All estimated for 2022
If the bank gives their OK, then the planning starts, it goes to builders and home builders...

A precise calculation is usually needed, but it also results from the planning.
P.S. Almost no house is turnkey. Often, the painting work has to be organized by yourself. Kitchen too. Etc.
With 2,500/sqm you are well off. But only for the house. No outdoor facilities, no additional construction costs.

Can you also give me information about how much a basement roughly costs. Location would be in Neutraubling. Regards Bettina

I think I have read several times that flat roofs with a slight pitch are the cheapest roof type.