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

At 1% interest, the repayment is €1,900. 3% is a good value, definitely, but it can also be lowered during the phase with children and raised again when the phase comes where both work full-time again.

Of course. I calculated with 1.2%.
I would be interested to know who actually raises it.
That's the same old eyewash as with the special repayments. Everyone talks about the possibility and wants to use it, but the fewest actually do it because the money ends up being spent on consumption.
do you perhaps have some insider info on this? I would be very interested. Thanks

Sure. I calculated with 1.2%.

I would be interested to know who is increasing it.
It's the same smoke and mirrors as with the special repayment. Everyone talks about the possibility and really wants to use it, but very few actually do, because the money ends up being spent on consumption.

do you maybe have some insider info on this? I would be very interested. Thanks

Our advisor said that nearly 90% aim for the special repayment but do not do it. Of course, it's also difficult to assess this figure, since in the current phase special repayments only make sense to a limited extent, depending on the goal of the investment or savings, etc.

But yes, as already mentioned... Whether you make special repayments, adjust the savings rates, etc., must be considered individually, and ultimately everyone has to admit to themselves what kind of person they are, or how frugal they are. Only then can you take on such a project – otherwise, you should leave it. If 3 vacations a year / a fancy car / pricey everyday items / expensive restaurant visits, etc. are more important and you do not want to give them up, then with such an amount, for example, you are definitely in the wrong place!!

First of all, where is the catch, the house is way too cheap. Or no garage and garden included? Earnings are not generous for such a high loan amount.

It clearly states that no garage is included! To your "way too cheap" I counter with the following example calculation:

150 sqm x €2200 = €330,000 10% incidental costs = €33,000 Basement = approx. €70,000 Photovoltaic = approx. €15,000 Outdoor facilities = approx. €25,000 Carport = approx. €10,000

Subtotal = approx. €483,000

The OP states a total of €618,000, meaning approx. €135,000 remain for the plot + development... with only 315 sqm that would be roughly €400/sqm. That is more than realistic and anything but "way too cheap." Even if we assumed €2500/sqm it would still fit (if the sqm price for the plot is around €280), especially since the OP even gives relatively concrete additional cost details on top!

It clearly says that no garage is included!
To your "far too cheap," I counter the following example calculation:

150 sqm x €2200 = €330,000
10% incidental costs = €33,000
Basement = approx. €70,000
Photovoltaics = approx. €15,000
Outdoor facilities = approx. €25,000
Carport = approx. €10,000

Subtotal = approx. €483,000,-

The original poster states a total of €618,000, meaning that about €135,000 remain for the land + development... with only 315 sqm that would be roughly €400/sqm.
That is more than realistic and anything but "far too cheap."
Even if we assumed €2500/sqm, it would still fit (if the price per sqm for the land is about €280), especially since the original poster even specifies relatively concrete additional costs on top!

The original poster buys from the developer, so everything is significantly more expensive than you calculated and he also has an additional €40k in expenses.

The rate is once again too low. It should be 3% repayment for that amount. That makes exactly €2000 + €400 monthly ancillary costs. If you can and want to manage that with 1-2 children over 26 years, then go for it. Otherwise, build smaller.

Why 26 years? Both are 32, meaning they still have 35 years until retirement age of 67! And what you always somehow don't factor in is that the rate is fixed. It doesn't change over the fixed interest period (let's say 15 years). Incomes naturally rise, if nothing gets in the way. Let's fast forward:

15 years with a repayment of €1,800 at 1% interest means with a loan amount of €553k (minus €18k KFW): 2.906% repayment and a remaining debt of €293k.

The couple is now 47 years old, earns double, and (without property value increase) has already achieved something. In the best case, the rate stays the same now, but they earn significantly more money. Important: They have already built up around €324k in assets (repayment) plus the equity of €120k, making €444k in the property, which (without increase in value) is worth €691k. Loan-to-value ratio now at 42% – great for a follow-up loan.

If you now (we're writing the year 2036) get a follow-up loan of €293,000 at 4.2% interest, you can take another 20 years and happily continue to repay €1,800, ultimately being debt-free in 2056. Or you increase the rate after 15 years and repay a bit more because €1,800 by then feels much less severe on the wallet.

My opinion: If you have saved the equity, you are also ready to tighten your belt over the next 15 years. That is, however, the big question.

The OP is buying from the developer, so everything is significantly more expensive than you calculated and he also added 40k€ in premiums.

I don’t understand the last part. I myself said that he even listed the premium costs separately... Even if it’s a purchase from a developer, the price remains realistic. The plot is maximally small, and he even listed the additional purchase costs separately.

A pure 618k without premiums and additional purchase costs is definitely not "far too low," I stand by that!