Land purchase of 319 sqm for 191,000 euros and house construction realistic?

Overall a tight squeeze. In the years without children, you should definitely do a lot of extra repayments.

A few details also caught my attention

Construction road 700€

That’s enough for one truckload of gravel. You don’t have much construction road, but the budget only covers the crane area.

Parking space 2,000€ Terrace 5,000€ Garden 2,000€ Fence 2,000€

11,000€ for the entire outdoor area. That can work with your own labor, but you won’t have much luxury. Don’t underestimate the small extras that always come up and what they cost.

Own labor 5% 20,250€

Are you including labor time here to get a better loan-to-value ratio? Or where does the own labor come from? What exactly do you plan to do yourself that is not already accounted for in the calculation? With wallpapering and laying floors, you won’t reach 20k. And for the outdoor areas, you only budgeted for materials, so you can’t deduct anything more.

Overall a close call. In the years without children, you should definitely make extra repayments.

Wrong. You need a liquidity reserve for the early years with children in order to be able to offset a cash flow deficit. But you don’t have that if you use the money beforehand for extra repayments. This sentence reveals the typical mistake in many financing requests: They only look at the term and possibly the initial installment, but not at all at the cash flow structure. To put it differently: No, the installment does not have to be covered at every point in time from the ongoing cash flow. And yes, it is actually advisable to initially stretch the financing to 40 years instead of 30 years. Today’s annuity might be only about half as high in real terms in 20 years. At the same time, both will be working again, at least almost full time, in 20 years. It only makes sense to plan for a nominally higher burden and repayment for a follow-up financing today, because your capacity will have overcome the temporary low with small children by then.

One note: You better hurry with the house construction if you actually plan to contribute your own work. With a small child, you can probably forget about your desired amount of own work (unless with a long double parental leave, but then you also have income losses that you need to consider). Unless you have a craftsman as a father who is looking for activities in early retirement.

Wrong. For the early years with children, you need a liquidity reserve to be able to cover a cash flow deficit. But you don’t have that if you use the money beforehand for special repayments. This sentence reveals the typical mistake in many financing inquiries: only the term and possibly the initial rate are considered, but not at all the cash flow structure.

That is not correct. The original poster writes that with one salary he could afford a rate of about €1500 and has a financing offer in this range. Currently, with two salaries, they could afford over a thousand euros more. For simplicity’s sake, let’s assume that’s true.
One should not squander this money or let it rot under financing costs and taxable interest in some overnight money account. A certain liquidity reserve is of course sensible, but the rest should go into special repayments.

Yes, a liquidity reserve usually costs money. However, one does not want to make any profit with it, as its purpose is insurance. Insurance against bad times and insurance against having overestimated the affordable installment in young years. Then it has to bridge these lean years. The amount of the liquidity reserve is determined by the amount of equity contributed. Due to their age, the first child is likely to arrive sooner rather than later. Prepayments before the birth of the child are therefore hardly meaningful; liquidity over a period of perhaps 1-3 years should already be reasonably estimated today. The purpose of prepayments arises after the end of the lean years with small children or, if you will, even during them, if, against expectations, there were additional inflows for which there is no other use.

By the way, due to the inverted yield curve (short-term interest rates higher than long-term interest rates), it is currently even sensible to leave your money in a daily allowance account and earn 4% interest. You just have to be willing to change providers 2-3 times a year to benefit from new customer conditions. That costs about half an hour. Taxes are also only due from an investment capital of 50k euros with an allowance of 2000 euros per married couple at an interest rate of 4%. The original poster is unlikely to have that. The current situation may be unusual, but it is reality.

Would try to optimize income. Less IG Metall, but work even harder, try to reach 40 hours or AT, and then it will work.

Then you can also afford children without worrying about shortages.