How do you take the interest into account from the purchase of the land until moving in?

That mainly depends on how the rent payment before moving and the annuity afterward relate to each other. If you move from a more or less small apartment to a detached single-family house, the monthly burden will increase significantly and it should not be a problem to pay the construction period interest from the current expenses (because together with the rent it is still less than the annuity to be paid in the future). However, if you have already lived in a rented house with a garden, the rent and the later annuity approach each other (or sometimes the rent is actually even more expensive) – in my opinion there is no reason why you should be able to afford both in parallel – and especially not during the construction phase, which is already stressful and generally expensive enough (little things for the house, quickly grabbing something to eat while on the sample tour, going through the car wash more often here, refueling three times more there, and so on).

Why? What's wrong with having the interest financed?

From my point of view, nothing at all with investment properties. But with private interest on penalty interest... I don't know. Everyone has to decide for themselves whether they want to finance something like that. These are simply incidental construction costs that you also have to keep under control. Everything additionally borrowed CAN worsen the interest rate. We cover that from ongoing income. That's about a washing machine in 3.5 months + rent of 900€ per month. Hopefully decreasing quickly. At least you have to deal with it if it can't be covered from ongoing income.

Roughly, my calculation looks like this:
Land 280,000
House 220,000
Tax, Notary 22,000
Additional costs 78,000
Total costs 600,000
Equity 70,000
Loan therefore 530,000

That will not work. The land is very expensive and the house is supposed to be that cheap? You won't get a house for 220. Where did you get this value from? At least 100,000 are missing...

That will not work. The plot is very expensive and the house is supposed to be that cheap? You won’t get a house for 220. Where did you get this value from? At least 100,000 are missing...

It’s probably only 110 sqm of living space :-p

Are probably only 110sqm of living space

Somehow, the 550k€ loans with a loan-to-value ratio of 105%-90% are currently increasing. I find that alarming.

I have a similar question:

We are planning to start construction from May 2019. We could finalize the financing already in December or only shortly before the start of construction. The interest-free period is 12 months, and the construction period is also about 12 months.

If we finalize the financing this year, we will pay interest on the undrawn amount after the 12 months expire. If we wait with the financing until April/May, the conditions could correspondingly worsen.

What are your experiences here, which option is better?