From 0 to 100 in 3 years realistic? | Building obligation

I would have said that this is not sufficient for Smarthome etc... in 2 years in BaWü...

Unfortunately, I also assess it that way, which is why I do not understand the repeatedly made assumption that we would want to plan a 200sqm house.

Without the land, there are still 600k left.

- 100k basement
- 60k ancillary building costs with basement
- 20k kitchen + furniture
-> 420k remain.

That gets me to a 140sqm house with good fittings.

So I find your planning quite realistic.

A loan of 500k would have been too much for me.
Now it depends on the exact timing and what can still be saved by then.
You are also simply still very young.

As written, calculate the loan amount with 1.5 salaries. Then you will also have flexibility as a family later on.

Are the estimated 3,000€ per square meter in BaWü really set too high?

Absolutely not. I’m building in the southern SIG area and the general contractor gets a good 400,000€ for a house with about 135sqm on a slab. Of course, some things are included that could be omitted or done cheaper (geothermal energy, KfW40+), but he also takes care of some things that are often passed on to the builder, e.g. earthworks, architect services, construction electricity. So the pure construction costs are still a bit under 3,000€, but that’s with prices from about exactly a year ago. In the meantime, it has become more expensive. And some things you won’t be able to save on, e.g. the photovoltaic system.

With an annuity of 3.5% and a loan of 600,000€, I come to 1,600€ financing costs + additional costs. Where is my error in thinking to come to 2,500€? The stated 750,000€ should be seen minus equity.

With a 600,000€ loan, 1,600€ rate is only just over 2% repayment, depending on the interest rate assumed. With that, you get a term of 35-40 years. Way too long. At 1% interest, after 10 years you would still have a remaining debt of 460k. Very risky if interest rates rise significantly in the meantime.
If you take a longer fixed interest period, then the interest rate increases accordingly and you barely repay anything. To make things worse, interest rates will probably rise, so in 2 years you will probably not get 1.0% but maybe 1.5%. And currently you have too little equity for the really good interest rates. So 1% is tendentially still too optimistic.
The mentioned rule of thumb of 400€ per 100k loan corresponds to a term of about 23-25 years. So absolutely not a short-term financing, but still reasonable.
6*400 are 2,400, with 650k it would be accordingly 2,600€ per month. 600-650k are therefore about 2,500€ per month.

A brief addition regarding the building obligation. It is defined as follows: "The plots must be built on with a building permissible according to the development plan and ready for occupancy within three years after the purchase contract is concluded."

For us, it was defined that we had to present a building permit after 3 years, and the house was to be completed after 5 years.
Perhaps you can speak personally with the town hall/authority to find out what the above sentence concretely means for you.

The sentence is clear. [Bezugsfertig] means ready for moving in. Floors, painting, all done.