Is the construction project affordable? 570 k€ loan with a 5300 € salary

Has the equity been accumulated?

Otherwise, it will be tighter with children. But it will be doable.

Sounds doable to me under the conditions for now, although the question is whether those are really the final costs.

How big is the property?: 315 sqm

Can you fit a single-family house on it? Or are the 150m2 including the 50m2 basement?

Properly saved equity, good household net income, financing amount in relation to income is okay, no children yet --> definitely doable :)

In such a case, cost transparency is extremely important - of course, another 100k shouldn't be added - so definitely review everything carefully again and check for any hidden additional costs - renovation needs or other issues...

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Can you build a single-family house on it? Or are the 150m2 including the 50m2 basement?

Answer:

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It is a new single-family house according to KfW 55 standard with 150 sqm living space + basement with air-water heat pump and photovoltaics with storage in Bavaria.
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Why does no one ask why the OP thinks they need a basement? :)
Is this now an existing property? Then the above question is unnecessary. Have you already been awarded the contract?

Is the equity saved or gifted/inherited?

Currently, it is representable like this, but with 1-2 children the party is over for the time being.

Answer:

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Why does no one ask why the OP thinks they need a basement? :)
Is this an existing property? Then the above question is unnecessary. Have you already been awarded the contract?

I would also build with a basement on the mini plot.

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On the mini-plot, I would also build with a basement.

But that also drives up the costs. And I don't find the household income that generous - even if the financing is feasible.

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That would leave a monthly surplus of €730.
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What if one salary is partially lost due to parental leave ...?

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What about having children? What additional monthly expenses should one plan for a child?

Well, that can really add up ... :D
(even if this answer may not seem entirely helpful)
How was it again? A child costs about €150,000 up to the age of 18 - or something like that?
Friends of ours (two adults with children who have studied) say: one Ferrari "runs" in southern Germany, the other in northern Germany ;)