Financial planning for new construction with good income and little equity

Something like that works. But only with proper risk tolerance (meaning being able to sleep at night despite everything), austerity ability/willingness (hardly any leisure spending for years), incredible diligence, and the willingness to ultimately fail miserably despite everything.

My income is similar, just distributed differently. That means there is a higher risk that it might not work at all. I have already put in a lot of personal effort and have reached the limit of my endurance. Fortunately, my father-in-law has been able to help me often.
My purchase price was cheap and was also built cheaply.

Since moving in, we still don’t have a proper parking space, entrance podiums, or a real terrace. The front yard is a mixture of gravel/sand/pebbles/weeds.
The baseboards are still not installed everywhere.
Photovoltaics, shed, carport, terrace, and canopy—all only later.
I’ll soon build a shelter from free wood from a neighborhood platform.

When in 7-8 years the first block of refinancing comes up due to the end of the fixed interest period, it might be that I will have to sell after all (of course, this also depends on interest rates and salary development).

Now comes the big but:
I already had a property that I could freshly mortgage, so practically equity (not entirely, because I still have to pay it off, but in my case the tenant does that).
At that time, I got significantly lower interest rates than now. On the other hand, my total volume is also higher.

But you are 10 years younger and don’t have a child yet. So if then, actually now. Once the child is there, the intensive personal efforts are no longer possible (it only worked for me because the child was already older).

Then I wonder if you shouldn’t be able to earn more in Hesse. You don’t say what you do for work.
Maybe first search for a new, better-paid job (both) or if you like the job, negotiate, get further training, and work towards a career plan.
Build equity (live as if you already had the big loan and the house costs). Then search again after two years.

Thanks again for all the answers. Personally, I now have a much better understanding of the situation and the dangers. What I will do with this knowledge - we'll see. Just a brief comment on this assessment:

Then I wonder if you shouldn't be able to earn more in Hesse. You don't say what you do for work.
Maybe first look for a new, better-paying job (both of you) or if you like the job, negotiate, continue your education, and work towards a career plan.
Build equity (live as if you already had the big loan and house costs). Then look again after two years.

came up several times in this thread = the mentioned income is not considered "good" in relation.
It will probably be the same in this context here; when it comes to building a single-family house, as I see it, different standards apply.
But it's really SAD and shocking. You are proud of yourself as an upstarter with a migrant background and Harz4/social welfare parents from a ghetto panel building estate. You check online income calculators to see that you belong to the top 10-12% of the German population.
Yet a decent house seems only within reach for the top 5%. Sad. Something is wrong here...

But it is really SAD.

Yes, unfortunately it is. But with €8k net in metropolitan areas, if you want to live near the center, it's no different or like in your case with €5.5k. I have several cases in my circle of acquaintances. They simply missed the right time to build or waited for a better opportunity and missed out.

Thanks again for all the answers. I personally now have a much better understanding of the situation and the dangers. What I will do with that knowledge - we’ll see.
Just a quick comment, this assessment:

came up several times in this thread = the mentioned income is not really what you would call "good" in relation.
This will probably also be the case here in this context; when it comes to building a single-family house, as I see, different standards apply.
But it is really SAD. You are proud of yourself as an upwardly mobile person with a migration background and Hartz IV / citizen's money parents from a ghetto prefab housing estate. You check online calculators for income, to see that you belong to the top 10-12% of the German population.
Yet a reasonable house is probably only within reach of the top 5%. Sad. Something is wrong here...

You are absolutely right...

My brother-in-law starts with over 60k after university and spends well over 30% of his net salary for his first own place relatively centrally in the city (BaWü - Stuttgart). It is sad what a cost factor a house/apartment takes nowadays, whether buying or renting.

Living in the middle of the city --> luxury
Own home --> pure luxury

Unfortunately it is like that... As you can see, even the top 10% earners can no longer necessarily afford it.

I would also exclude outdoor facilities from the financing if that makes the difference between hop or top. There's sometimes an insane amount of money flying around.

I would not estimate construction costs below 3,300 (excl. ancillary construction costs). That would then be just over 450,000 for you, conservatively estimated.

At just under 4% interest, that's about 2000€ per month for interest and repayment. If you calculate with a salary of 4000€, you have to want that.

In this region, where land is so cheap, I would look for an older house, even unrenovated, move in first and then see. There should definitely be something around 180,000 to 200,000.

Best regards

(...)
But a sensible house is probably only achievable for the top 5%. Sad. Something is wrong here...

No. A house that is considered "sensible" here is indeed only possible for the top 5%. But what can you do... if you can't afford food at Kevin Fehling (3 stars), do you then starve voluntarily?

You don't need a garage or a carport. The terrace doesn't have to be finished when you move in. The garden doesn't have to be done by a landscaping gardener. You can also shovel away 6m³ yourself. You can even shovel 50m³ yourself. You can also plant a hedge yourself. It's all possible. People used to do that in the past, there was no excavator for the garden then.

And do you know what? I have been living for almost a year in a house from Town & Country. With fittings from Vigour, with tiles for 30 EUR/m², with a pretty big kitchen from Pino, although to be honest, it cost more than 10,000 EUR, but with a U-shaped layout including a bar, it was hardly possible otherwise. Of course, the garden is still a poppy meadow at the moment, I'm going to plant the hedge this weekend as 60-80cm balled plants. 45m for 1,300 EUR including delivery. For that, the landscaping gardener wouldn't even plant 10. Painting and floors done by myself, except for 60x60 tiles in the kitchen and hallway.

The only thing I've outsourced outside so far was the connection of the downpipes to the cistern. And the civil engineer screwed that up right away; one of the pipes is leaking. We've been arguing for months because he neither wants to open it nor put a camera inside.