Can we afford to build a house?

@DaSt
On the topic of parents-in-law:

aside from the fact that I don't want mine in the house :)

If the parents-in-law have some money saved up, there is also an option with a lifelong right of residence.
You grant them a lifelong right of residence (in the land register) and receive money for it accordingly, which you can use as equity. Alternatively, a loan from the parents-in-law would also be possible, where you offset the installment with the rent.
Advantages and disadvantages should be clarified with the tax advisor, as the topic of income from renting and leasing also plays a role here. There was a change in 2012 regarding the minimum rent that must be charged so that expenses are recognized.

On the topic of house price: we plan about 125m² including ancillary building costs without land for our house with 227T€.
However, it will not be a KFW house and initially without a garage. We also want to take furniture including the kitchen with us for now.

@Der Da

Our kitchen without refrigerator cost about 2000€ including assembly about 4 years ago at the furniture discounter ;)
That was a special offer kitchen. Still, we could change everything individually. We already had the fridge-freezer combo and the microwave, so we invested the money in the other appliances. So the remaining appliances became decent no-name products.
This is not a high-end kitchen but has everything we need and still looks great after 4 years.

Well, our kitchen in the rental apartment only cost 2500. But we cook way too often with it. The oven doesn't hold the temperature, the dishwasher is loud and doesn't dry properly, the exhaust hood is a noisy light source... suction effect = 0, and the gas flames go out at the slightest draft.

Sure, you can also buy a kitchen for 5000 that is somewhat suitable, but shouldn't you treat yourself to something, especially with such an expensive piece of furniture when the rest already costs almost 300,000? The additional 5000 really doesn't make much of a difference :)

But that's a personal decision. I just wanted to express that you can easily go wrong with the dream house and the dream kitchen... I also wanted 8000€. The first visit to the kitchen studio then said 23,000. Ouch... now it's just under 11,000, but with everything that goes with it (for us).

Kitchen is a topic in itself.... I myself have a kitchen in my current rental apartment for ~5-6k

~2k cabinets from Ikea, ~2.4k appliances (good appliances! Siemens A+++ refrigerator, Siemens induction cooktop, Neff oven, etc.) just under 1k countertop and everything self-assembled...

However, if you get it offered at the kitchen studio including installation, you end up at 10k+...

Many kitchen studios simply try to fool customers! They then calculate with 20k+ and then you luckily get a discount so that in the end it’s 15k... But the kitchen itself is not worth 10k...
generally, with a kitchen offer you should first subtract the electrical appliances, then you can estimate the cabinets + assembly costs based on Ikea prices and then in the end you see whether the kitchen price is justified or not....

if the difference is now 8-10k you should really ask yourself whether the cabinets/fronts are so much better than the Ikea parts... because assembly costs should be similar and you can find the prices for electrical appliances on the internet...

@ The Da:
That’s why my question about full financing: I know myself that with such a sum, 20k is pocket money – I’ve also gone to buy bread before and have some idea what the € is worth.

I have been living with my own household for 12 years, so I’m not starting from zero (although in those 12 years living alone in 3 apartments combined, I haven’t spent 20k on furniture yet). I have a complete kitchen with all very well functioning electrical appliances. The furniture would also be "still usable" for the time being. Honestly, the kitchen worries me the least; in the worst case, I could start with the old one. Of course, I won’t order a kitchen before the building is finished and standing there.
The same goes for the child – if I felt financially unable to cope, I certainly wouldn’t bring a child into the world...
In general, I am a very cautious person when it comes to money, which is why I try to get constructive opinions / suggestions & ideas in forums like this one.

Regarding the parents-in-law: I have a very good relationship with them, so that’s not a problem. When a child is there, they would come by daily anyway and hang out at my place, so it makes more sense if they just take the little one and disappear over there...
Furthermore, the granny flat is, of course, planned to be 100% autonomous and would also be rentable to a future unrelated tenant. Apartments in our area are very popular, so I’m not worried for now that we won’t be able to rent it out later. The rental price here has risen by 53.6% in the last 20 years (source Federal Statistical Office).

All in all, I gather from your statements that in your opinion, it is not possible with this salary. That was all I wanted to know.
How much does one have to earn to be able to afford such a house? Not everyone inherits 100k or has nice rich families who give them the money, and yet around 50% of German citizens are homeowners...?

A few questions upfront
What rate did you have in mind?
Why is there now no more than 20T€ equity left?

I think with the income and rental income it is not impossible to build, but of course you have to watch the costs.
There is so much beautiful stuff you can install in the house, but everything has its price.

We earn a little less than you, but have around 60T€ equity.
Our planned construction costs including the land are 270T€, although the land costs here are still moderate.
Garage, kitchen etc. will be postponed for now. If our planned buffer is not needed, the garage will come right away, if it is needed, it will come later.

The home ownership rate is 45%. But this also includes condominiums.

Saving money by itself for old age makes no sense in my opinion, because no one knows what inflation will look like...

*clears throat*

Owning a paid-off property is certainly a good component of private retirement provision, but I wouldn’t go so far as to say you don’t need to save anything else...

Whether the well-known "riester" pension is the best solution is another question...

And if inflation picks up, normally interest on deposits does too...

Building is certainly possible... only the current concept might be somewhat suboptimal...

Don’t the parents-in-law have any savings? Instead of paying you 600€ rent (which you might have to declare as income depending on the situation!) they should rather pay you, for example, 40-50k... you use this extra equity to reduce the interest burden on your 140m²... finance most of the 60m²... ideally with 2 separate contracts that you can repay independently....

Then repay your 140m² somewhat faster and initially keep the 60m² at only 1% interest! You then charge your parents significantly less rent (but it must not be TOO low, otherwise the tax office gets suspicious!) e.g. 300€

The background is that you can offset the rental income against the interest burden for the rented apartment... if you pay 300€ interest and receive 300€ rent, then you don’t have to pay taxes on the rental income! If, for example, you only pay 200€ interest for the 60m² and collect 600€ rent, there is a 400€ difference that you have to declare normally...

That’s why you should put repayments and equity as much as possible into your part and keep the rent rather low...