Is financing a new building feasible?

A small car costs about 12,000 euros, with 60 months RND (great if it lasts longer) that makes 200 euros/month, tax and insurance are another 50 euros/month, every three years 900 euros for 8 tires is also 25 euros, inspection is 300 euros per year, so also 25 euros. 100 euros for fuel... That’s already 400 euros per month. Anyone who claims that a car costs less than 250-300 euros per month simply cannot be taken seriously, unless the car is deregistered in the garage... Oh yes, such a garage also costs money, as does washing, antifreeze and many other small things.

Which small car still costs 12,000 euros? Even a Polo or Fiesta, reasonably powered and equipped, quickly costs 18-20k euros, not to mention the A1, etc... Insurance strongly depends on the SF class and with a new car, comprehensive insurance is practically mandatory, especially if it is financed.

A car costs an average of €509/month. This includes a new purchase as well as taxes, insurance, maintenance costs, or tires/tire changes. However, you have calculated the housing costs very high. One usually estimates €2-3/sqm. Read the pinned post by tox... and calculate again

Regards

No one wanted to believe me again

So I even have to take my car to the [TÜV] every two years... It is also easily forgotten!

So, you should definitely have the real costs in mind, at least for yourself. They can also fluctuate, as in the case of @TE who does a lot of work himself, or depending on the size/segment of the vehicle.

Otherwise, it will simply become tight at some point when replacements have to be purchased. I believe that regarding this particular aspect, is sufficiently sensitized.

Banks approach the topic differently. Some have special flat rates in the calculation of debt service capacity, others have already included the topic of mobility in the actual household flat rate (for one car).

However, the depreciation is not always included in the bank's calculation in this calculation, only insurance, operating costs, and repair shop costs.

Including insurance, taxes, depreciation, inspection, repairs, fuel...
May I ask which cars these are, how old they are, and how much you approximately drive per month?

Sure. The first vehicle is an Astra, year 09, bought as a one-year-old car. List price ~24,000€, bought for 12,000€ from the dealer. Current value about 5,500€ with now just under 100k km on the odometer.

Depreciation thus 77€ per month converted
Insurance comprehensive + partial coverage 250€ p.a. / 21€ p.M.
Tax 108€ p.a. / 9€ p.M.
Inspection/TÜV every 2 years ~300€ or 12.50€ p.M.
Unexpected repairs about 1000€ / 12€ p.M.
Wear repairs about 500€ (set of tires, one time brakes) / 6€ p.M.
Fuel 7,000 km p.a. at 1.30€ and 7.5l = 57€ p.M.

makes 195€ all-in per month.

Second vehicle, a van for the family, looks similar, is driven even less during the week, but overall has a bit more mileage p.a. because of trips on weekends etc., but was purchased cheaper in terms of investment. Nice, used retiree vehicle with some paint chips, but low km and top condition (garage-kept, continuous service book etc.). Currently higher residual value so there is still comprehensive insurance here, but the comprehensive insurance adds more (relatively poor no-claims bonus on the second vehicle) and the partial coverage has a 1000€ deductible because it should only cover total loss, scratches do not matter to me and are not economically worth covering through insurance anyway.
It could be that it is just over 200€ p.M., but so far there have been no major repairs. Vehicle history is flawless and completely documented, nothing had to be done except normal wear and tear.

A small car costs about 12,000 euros,

Sure, if it is (almost) new and/or from German brands, that's true. But it is also the most expensive option.

at 60 months RND (great if it lasts longer) that makes 200 euros/month,

Eh? 5 years of lifespan for a 12k small car and then it is worthless? Completely wrong. Especially small cars are surprisingly price stable because they are in a lower price segment.

tax and insurance are another 50 euros/month,

yes, with full coverage. Understandable with a new car, but not applicable if you drive older vehicles anyway.
Or the tax hits hard because you drive diesel.

every three years 900 euros for 8 tires are also 25 euros,

The interval of course depends on usage, I recently came to 7 years. My new tire set (summer tires) including mounting on the existing rims just cost 280€, not 450€ as in your calculation. 16 inch wheels, ADAC top 5, so no cheap Chinese stuff.

inspection is 300 euros a year, so also 25 euros.

I don’t know anyone who goes to inspection annually unless a new car warranty forces them to. Waste of money. Oil change costs 30€ material, labor 50€. My cars go to major inspection and TÜV every two years and actually come to about 300€. I always bring my own oil (Castrol Edge or whatever), workshop prices are insane.

100 euros for fuel...

Usage dependent. No sales representatives in the family. Short commutes save time, money and quality of life. That’s why I have moved a few times already in my life.

Anyone who claims that a car costs less than 250-300 euros a month simply cannot be taken seriously, unless the car is de-registered in the garage... Oh yes, such a garage also costs money, and washing too, antifreeze and many other small things.

It’s a shame that you see it so narrow-minded. There are people for whom cars are not a hobby, toy, or even a status symbol (I don’t want to imply that about you here). Those who are not commuters or who don’t like standing in traffic jams (-> NRW).
There will actually be no garage in the new house, probably (double) carport. Simply because the costs for a car house are so absurd just to put a car in there.
Washing is done three times a year. Before winter, after winter, and once in summer. That’s enough. Silver and co. are undemanding colors and I do not lose face if the car sometimes has no wax on it.

Which small car still costs €12,000? Even a Polo or Fiesta, reasonably powered and equipped, quickly costs €18-20k, not to mention the A1, etc...

Pretty much every one, except the ones you mentioned. You can get a Kia Picanto new for that money, it has a 7-year warranty, and on the secondary market it goes for insane prices (hardly any depreciation). The French cars are cheaper, with average equipment they are under €10k new.

If you don’t want to pay less for a car, that's fine. But please don’t act as if it can’t be done differently. You’ve set that limit yourselves.

What kind of equipment MUST a Fiesta have, because otherwise it’s probably not a real car? A nice €2k built-in navigation system and leather seats? Because how exactly does that endanger quality of life for short trips to the bakery or workplace?

Sorry, I’m slipping into assumptions. I just find it so absurd.

But what can I say, instead of a garage I’m getting a Jacuzzi placed on the terrace. I’ll be splashing around in it (and not my car)