Building a house - Is the budget for building a house okay? Who has experience?

Hello everyone, I have also been following the forum for some time now and slowly I have to decide whether to build a house or not. I think you are exactly the right people to give me good advice.

The following initial situation:

Region: NRW, Hagen or Schwerte
People: wife (30), me (30) and son (1) family planning completed, 2 nearly new cars
Income: wife 30 hours and me full-time with child benefit = 3800€ net
Equity: 110,000€ = 75,000€
minus 25,000€ kitchen and furniture
minus 10,000€ reserve?
Own work: wall and floor coverings (except bathrooms and kitchen because of tiles), insulation (cut and stuff in this glass wool), lay underfloor heating

Monthly expenses as I imagine them: (if something is missing or too much, feel free to correct)

House: estimated
Loan: 800€ (approx. 240,000€)
Electricity: 90€
Gas: 140€
Water: 50€
Internet
Phone: 60€
TV
Cable fee: 6€

Garbage / property tax: 120€ estimated
Sewage

Insurances estimated
Household contents: 60€
Building insurance: 40€
Legal protection: 20€
Term life insurance: 24€
Liability: 10€

Food currently
Food and drink: 500€
Mobile phones: 70€
Fitness: 40€
Clothing and others: 300€
Savings: 200€

Cars currently
Insurances: 120€
Tax: 20€
Fuel: 200€
Repairs: 50€
---------
2850€
+ vacation 250€

=3100€

Land costs with us between 220€ and 300€
I think about 350 sqm should be enough, we are not blessed with a green thumb but a terrace with table and some lawn for a large paddling pool should definitely be there.

So you can reckon with about 100,000€ in my opinion.

So now, the question: what kind of house would I like:
Guest WC, wardrobe that is not visible, open kitchen, open living and dining area
Bathroom, bedroom, dressing room, children's room (should be at least 15 sqm), small office

Attic, basement or elsewhere, I would still like a room for weight bench, dryer, washing machine and maybe later a sauna
Garage or carport does not matter, main thing is a shelter and a parking space.

Now the question for you, is it possible or is it better to consider an existing property?

Thank you very much

350m² is too little for a detached house.
I find an 800€ installment very tight, even though interest rates are currently at rock bottom.
2.5% interest + 2% repayment is around 900€.

Regarding the cars:
Do they also have to be replaced sometime in the next 20 years?
50€ for repairs, tires, maintenance, etc. for 2 cars?

60€ for household contents I think is too much.

Otherwise, I hardly believe you will make it with the budget and your wishes.

240T€ + 75T€ = 315 T€
minus land >100T€
minus garage/carport 10T€
minus incidental construction costs 30-40T€
minus painting work 10T€
leaves 155-165 T€ remaining.

I agree with Musketier. The targeted budget and the targeted rate will not be sufficient.

What I notice at first glance:

Kita costs or daycare provider?
BU insurance?

A detached house is also possible with 300 sqm! It depends on your own requirements and the location of the property! 500 euros for food is too little. Among other things, retirement provision, property tax...... are missing. Own contribution does not include materials!

With food and drink, it's simply the current situation. For me, a small company pension of about 600€ would come later, otherwise our house should be our retirement provision. My problem is quite simple, at the moment we live quite cheaply and save about 1500€ a month, this list that I have put together still includes a savings rate of 700€, which I find acceptable. But if you say, for example, if you buy/build a house then 200€ a month is also okay because many have that, I would accept that.

Rule of thumb is to set aside reserves for the house of 1.5% of the production cost per year. The more, the better, and it depends on your living habits

Corrected twice, I wrote nonsense