House financially feasible at about 5,000 net?

Basically: a 400€ installment buys you a 100k loan. If we assume a 2000€ installment, that means a budget of a good 500,000€. You can build with that if the plot of land isn’t too expensive and you skip the big money-eaters like the basement and garage. At your young age, you can also stretch it a bit and borrow more if necessary to fulfill your dreams.

For your financial planning, I would recommend being a bit more honest in your calculations. Cars also need repairs from time to time and always depreciate in value. That must be included in the plan. Being debt-free is nice and all, but without a savings rate for the car, it’s easy to paint an overly optimistic picture.

about the cars:
Car 1:
paid off, 2 years old, comprehensive insurance 500pa, taxes 100p.a.
I now work a lot from home, otherwise I have a distance of 8km, so I don't even refuel every month, therefore an average of 50 euros monthly

Car 2
paid off, 7 years old, partial insurance 300 p.a.,
taxes (approximately) 100p.a., fuel costs about 70 euros/month, about 15km distance.

These are the numbers that result for me, unless I have miscalculated.

You have not miscalculated. But the calculation is missing variables. The cars require tires, maintenance, repair.
For us, cars incur almost identical 115 EUR fuel/month, 205 EUR for their upkeep.

EDIT: However, it was a rather unfavorable comparison period, in which larger services and two sets of tires were due.

To be able to assess this, I specifically lack your plans / the price level where you want to buy/build.

I agree.

With a net income of 5k, financing 450k is more feasible than 650k, so I would also first look at which price range your own house wishes fall into and then see if they can be realized with the income.

A single-family home should be feasible; whether a new build is possible depends on the land prices. Just start looking for land and existing properties that you like and diligently save alongside. A bit of a salary increase is surely still possible as well.

Clearly doable!

There is a sticking point you need to watch out for, or that could cause you "problems":

- Children: as the main breadwinner, you will initially be out of action – then money will become quite tight. There is a buffer in the form of stocks in the equity assets --> check whether these might be cashable or whether it is worthwhile or if they are really invested for the long term.

There are clearly more positive points in favor of a home:

- you are still young and can easily pay off the loan for 40 years until retirement
- salary trend according to your statements is clearly rising
- no children yet, which currently makes it easier for you (financially and in terms of burden)

I would advise you to make sure that your salaries keep rising "day by day," so that before the first child you both have a decent salary (even more important for the man than the woman), so that the monthly repayment burden is manageable, even with a child.

Save up a good amount of equity over the next approx. 2 years (depending on how long it takes you to move into the home), as much as possible, and set aside a buffer for the times with a child and one income --> this gives security and prevents you from getting into trouble.

Make sure you do not bury money unnecessarily in the house... better to build somewhat smaller and forgo some frills than to struggle with the repayment amount for the next 20 years.

See how things develop in about a year. Keep a household diary and try to avoid unnecessary costs. Try to save diligently and see what is realistically feasible monthly and what is not.

But otherwise... it should work!

Income: 4900

There are rough rules of thumb, such as the maximum loan amount should not exceed 100 to 110 times the net income. So a bit over €500,000 in loans plus equity is easily possible. Now of course we don't know where and what you want to build. You did say NRW/OWL, but how much do plots cost there, how expensive is the square meter, how large should the plot and the house be?