Affordable homeownership: Buy or pre-fabricated house?

The bank (I work at one) will look at the figures from the last 2-4 years, not just 2017. The administrative effort is quite high for self-employed and freelancers, so for the initial meeting, better bring more documents, including those about retirement provision, tax office, etc. And bring enough time. The upcoming civil servant status of the woman is of course a big plus. However, you will certainly be asked about family planning, and you should already have a convincing and well-thought-out answer ready. Just as a tip. (We have already had couples with a newborn where the woman freely said that she wants to stay at home until the transition to secondary school... that is obviously fatal).

No, of course there were other expenses as well (car, vacation, etc.). The 10k is only from last year.

After taxes, about half is gone. The reserves for the company are there, so they don't need to be accumulated further. Currently, we pay around 700 EUR rent. However, I would prefer a longer term with smaller installments (so around 700 EUR/month).

Thank you for the tip. I already knew about the documents from the last years. All figures are good - active growth. Children are actually not planned/here. Therefore, the topic should not be a big obstacle. However, I thank you very much for the insight from the other perspective!

We also wanted to buy at first, but then decided to build a house because here (rural in Hessen) only very old houses are for sale, so a lot of money has to be invested or new houses, whose purchase price is almost as high as a new build, and since plots here are still cheap, we preferred to build new according to our ideas.
However, a prefab house does not necessarily have to be cheaper than a solid build.
By the way, I grew up in a terraced middle house where, "to make matters worse," the living/dining room also faced north and I can't quite understand why so many exclude that. I never found it bad, and it even has heating advantages.

By the way, we only brought in 21 thousand euros of equity and currently only my husband earns and he has a fixed-term contract (teacher)...nevertheless, we easily got a good loan.

Your wish for a €700/month rate and €10K equity honestly won't get you very far. You also have to plan monthly savings again for vacations and a new car, or your car lasts the next 30 years and you don't go on vacation anymore. But that actually doesn't matter, the bank applies fixed amounts there. And a €50K annual salary is not that great for self-employed, since the risk of loss of earnings is much higher than, for example, for a civil servant.

Impossible with the equity