Is financing possible with ING?

Wow, I hope for you that the bank rejects this. There is practically no more risk than what you want to "take" with this project. This is not meant to be offensive or an attack, but a fact that you have to face.

Loan amount €499,000. 1% repayment with options for special repayment and adjustment of the rate upwards. 20 years fixed interest period and loan interest rate is 1.3%

LOL - I would be happy if you get the loan. I can name 100 banks off the top of my head that wouldn’t do it. And rightly so.

As I said, these are the promotional prices for the town villas completely turnkey without interior finishing.

Buy the promotional kitchen too. It’s available with a 70% discount. Plus a dishwasher for free. And you believe all that?

I don't understand how a monthly payment of €970 + €500 additional costs (which will, however, come up in 1-1.5 years when the house is built and we have moved in, and after my husband has potentially increased his net salary by another €200-300) can ruin our lives so much.

The monthly payment won't ruin you either. It will be the need for additional financing. And your gullibility.

Loan amount €499,000. 1% repayment with options for special repayments and increasing the installment. 20 years fixed interest period and the loan interest rate is 1.3% (I don’t know the exact value off the top of my head). We are aware that 1% repayment is nothing. And you should start at least with 2%. But we planned it like this for the first period as long as the baby is small and I maybe don’t work at all or earn max €1800/month. As I said, we have completely left out my husband’s self-employment, but something like that would be intended for special repayments until we both can contribute more again and increase the repayment rate.

You would still have €380k loan outstanding after 20!!! years. And maybe a second child is coming? Children’s desires grow over time. So we start with the same net income with €1800 installment (plus €25k special repayment option) and that again shows that maybe you are not ready to give up enough else for the house.

Overall, I would be very surprised if this would get approved precisely at the Ing-Diba. A colleague of mine with €6k net and almost €100k equity is currently having difficulties getting a €600k loan. But he wants to build a 120sqm semi-detached house, where the €600k should at least hopefully be enough.

The question I would like to ask is, do you see any obstacles on the way to approval from the bank? How high is the chance of approval or the risk of rejection considering our current finances?

That was your original question to which a response was given. ING is currently cherry-picking, or rather just doing the standard. Recently we had a thread where the advisor was very sure that ING would give the green light. Nothing came of it. So yes, there are some obstacles here. I understand that you don't want to read this, but I believe you know very well that it will be tight.

I just don’t understand what this has to do with my actual question

You know that yourself. Otherwise, you wouldn’t be nervous and wouldn’t be asking here either.
I am not a financial expert here either, but I can do the math.
For example, I can see that if you have 30,000 liquid funds, of which 20,000 are included in the financing, there are still 10,000 left, which should cover a) purchase incidental costs of over 13,000, b) kitchen 15,000 and c) buffer.
Then there are own contributions, which have a value of 48,000.
I’ll put it like this: this 48,000 is missing. And that’s where the bank advisor asked whether it’s possible for you to plug this gap through own contributions. That’s how it’s done, although not usually in this magnitude.
The material and labor time, whoever bears them, must be provided by someone or paid by you.
These are simply facts.
And just because it is a developed plot, utility connections still apply.
Also, the construction service description must be checked. These days, there are constantly threads running about the topic of services. And especially cheaply calculated houses have a construction service description that unfortunately is not sufficient.
It starts with the 30cm earthworks, goes through excavation disposal etc., and continues with missing electricity, LAN, entrance canopy, water storage, etc. You can calculate it nicely, but the bank doesn’t. And if it’s covered by the 48,000 own contributions, this will become a personal problem for you if these costs arise.

Surely there are fewer trips or fewer silly expenses because all the earned money flows completely into the house.

Do you mean prepayments? Surpluses are needed for purchases in the first years, anyone who has built with your means can confirm that here. Outdoor facilities... paving work, splash protection... that’s not for free. And yes, you can do it little by little yourself, but even for a construction person that costs money.

The house is not a shell house but a turnkey house without interior work. We left out interior work such as tiling, painting, sanitary because my husband gets the craftsmen as well as the materials for that.

See above.
Please name the builder (no link) or/and post the construction service description here.

Regarding construction costs: the turnkey house in solid construction costs 225,000€ without interior work (special price).

Is it being built in BB?

Since my husband comes from the civil engineering sector and also has his own executing company in construction together with his father, we planned and declared own contributions in the amount of 48,000€.

Equity: 30,000€ in the account. Of that, we declared 20,000€ as equity.

Purchase incidental costs (notary, GES): 13,800€ (we will pay that from equity)