What house construction options are available under these conditions?

Then I'll build a fantasy house now, okay?
Plot 500sqm * €300 + additional costs = €160k
House 170sqm * €2000 = €340k
Large garage OR basement = €40k / €60k ~ €50k
Additional construction costs + ceiling + floors + buffer + exterior = 40 + 15 + 15 + 20 + 20 = €110k
Total = €660k
To finance €610k

With 20 years fixed interest one gets:
2.11%/year
€2100/month
+ €350 additional costs
= €2450/month

And after 20 years there is still a residual debt of €300k!

1/3 of your monthly income = €1933
And from here it hurts.
Personally, I would save until you break the 80% threshold and then build.

Hope I could help a bit
(all subjective - there will be people who say “that’s all calculated too expensive” etc.)

Now don’t scare him. The calculation still has to prove itself. I see some numbers as fixed. But we/you are already below the stated numbers with a few exceptions.

Plot 500sqm * €300 + additional costs = €160k
House 170sqm 140sqm * €2000 = €280k
Large garage OR basement without basement but with carport including tool room = €15k
Additional construction costs + ceiling + floors + buffer + exterior = 40 + 15 + 15 (I consider this exaggerated, as some of it is already included in the first two positions.) 25 + 10 (painting + plastering) + 10 + 20 + 20 = €100k €85k

Total about €540k
Here I would also only count the immediately available capital as equity.
Thus you end up at €495k with a buffer that will be lost anyway.

That is €100k less than the mentioned €600k, as the house is smaller, but still €100k more than you imagine.

No matter what you think now, but at the current construction prices the plot is definitely too expensive and that was still the municipality’s price! The kids are still coming and you are roughly looking at a rate over 20 years and 3% repayment of €2000 + €400 monthly additional costs.
I can think of better things!

Alright, thank you very much for your input. I had a rough idea of which direction this is going, but it's good to have it confirmed once again (multiple times). I would like to wait longer to build the house, as you already suggested, until a proper amount of equity is available. The problem, however, is that – as a user here already noted – the desire to have children will probably come sooner than the house. Our apartment is only 70sqm (including sloped ceilings), with a child it will already be tight. With the 475 euros warm, we really have a bargain here and a great landlord. If we were to move now and get a bigger place (80sqm+), that would also cost some investment (we can’t take the kitchen with us) and the rent would rise to at least 800 euros warm. Anyway, that’s just some background information.

All right, many thanks for your input. I had a rough idea of the direction this is going, but it's good to have it confirmed once (multiple times). As you already suggested, I would like to wait longer with building the house until a solid amount of equity is available. However, the problem is - as one user already pointed out - that the desire to have children will probably come sooner than the house. Our apartment is only 70 sqm (including sloped ceilings), with a child it will already be tight. With 475 euros warm, we really have a bargain here and a great landlord. If we were to move now and get bigger (80 sqm+), it would also cost some investment (we can't take the kitchen with us) and the rent would increase to at least 800 euros warm. Anyway, just a bit of background information.

We will certainly hear/read from each other again on this argument ;-)

All right, thank you very much for your input. I had a rough idea of the direction this was going, but it’s good to have it confirmed once again (several times). As you already suggested, I would like to wait longer to start building the house until a decent amount of equity is available. The problem, however, is that – as a user here already noted – the desire to have children will probably come sooner than the house. Our apartment is only 70 sqm (including sloped ceilings), and with a child it will already be tight. With 475 euros warm rent, we really have a bargain and a great landlord here. If we were to move now and get bigger (80 sqm+), that would also cost some investment (we can’t take the kitchen with us) and the rent would rise to at least 800 euros warm. Anyway, that’s just some background information.

I just want to point out that a child in the early years can certainly be happy without having their own room... some even consistently refuse having their own bed. I don’t know your apartment but I just want to say that the nowadays common opinion that a child has bad parents because they don’t have their own playroom etc. is complete nonsense. Our current apartment wouldn’t be enough in the long run with a child either, but until we move into the house, it will be more than enough here (we expect to move when our daughter is about 2.5 years old).

Our apartment is only 70sqm (including sloping ceilings), with a child it gets tight. With the 475 euros all-inclusive, we really got a bargain here and a great landlord. If we were to move now and get bigger (80sqm+), it would also cost some investment (we can't take the kitchen with us) and the rent would rise to at least 800 euros all-inclusive.

It was the same for us, but a small child doesn't need much space at first. I would continue saving now and start looking for plots or existing properties. Use contacts and don't rush anything, but be ready to act quickly if a good opportunity arises. Keep an open mind about everything.

How many rooms do you have?