Are we crazy? Is this doable? Risk too high?

Banks conduct an actual valuation. Houses that might be inherited someday, potential rental income, or presumed salary increases are of less interest there.

By the way: before you can ever rent out the parental home in xx years, you will probably have to invest xxx,xxx€ in maintenance/renovation/refurbishment beforehand. But that's simply not the topic here, you can completely leave that out.

Who owns the building plot? Only that person will have a chance of obtaining construction financing. That means the first step would be to have the ownership structure changed accordingly at the notary, e.g. 50:50 you and your brother. The bank will then consider the plot as equity, provided a reasonable value can be determined, which depends on location and condition. 11.5x70m doesn’t sound exactly optimal, did you buy an old street or what?

Depending on how the plot is valued, the bank will decide whether the income of the borrowers is sufficient. Possibly a guarantee from the parents who secure with their house. I suspect the only solution will be two separate loans for each semi-detached half per couple. But of course I don’t know whether semi-detached development is possible. What does the preliminary building inquiry say? Every bank wants to see that first anyway.

The question of whether partners should be included in the land register or not is irrelevant. The two siblings bring in the property and have the responsibility with the loan. The life partners have no risk and pay their normal share of the rent. They have to pay that anyway in the rental apartment. If the relationship ends, the responsible parties can pay the installment themselves. Done.

If the life partners absolutely want to be in the land register, they can buy half of the property and pay accordingly. Provided the siblings want to sell. Then it would be a different story and everyone would be listed in the land register. However, I would not recommend this option in your case.

So, from the constellation, I don’t find it problematic at all.

Price-wise, of course, it’s quite a statement. At that age, such figures... phew... If, of course, an inheritance comes (regardless of the house), which no one should count on, blah blah, it’s different. But still... it’s quite something to have 300k debt at under 30 and tied to the place.

Definitely doable. But from today’s perspective, I wouldn’t do it. But hey, everyone is different.

The life partners have no risk and pay their normal share of the rent. They have to pay that anyway in the rented apartment.

The comparison would only make sense if such a rental apartment also belonged to the partner.

If I waive any ownership rights to a house that my life partner calls "our" house, I want to only have to pay half of the additional costs. You "rent" from business partners to whom you help pay off the loan through the rent. But you don’t do that with your own life partners. I consider the dual role of life partner and business partner unhealthy.

The question of whether a partner should be included in the land register or not is irrelevant. The two siblings bring the property and have the responsibility with the loan. The life partners have no risk and pay their normal share of the rent. They have to pay that anyway in the rental apartment. If it ends with the partner, then the responsible parties can pay the installment themselves. Done.

If the life partners absolutely want to be in the land register, they can buy half of the property and pay accordingly. Provided the siblings want to sell.

How do you know who is listed in the land register? Did I overlook something? Maybe just one of the brothers, or the dad, or the uncle?

Your approach is nonsense because the life partners would then have to be compensated for their own contributions, since otherwise they would have nothing from the value increase they themselves created on the property.

At 600k the bank wants to see at least about 2000-2100€, less is not healthy and will at the latest become problematic with the follow-up financing.

That is roughly 1000 euros + m2 x 2.5 euros for incidental costs

Living expenses about 600 euros per person so about 1200 for 2 people.

Do you have a car loan?

You should also build up reserves and children will come too.

So think carefully about what you want to commit yourselves to.

My girlfriend and I live in a rental apartment: 750€ warm

Always calculate cold.

My brother and I thought of a rate of “only” 1400€ monthly

Each or together?

We have already had the parental home with the property appraised by the local court, we wanted to sell it in about 30 years in the interest of our parents to pay off the mortgage.

Are the parents still alive? If yes: The house is their retirement provision, not yours sons'.

It was appraised at 201,000€. In our opinion, the value is 30-50% too low compared to other houses offered.

Yes, everyone thinks that, and so everyone prices their house higher. The sale price usually doesn’t end up that high because the appraisal values also come up at the negotiation table. You only see what’s on the internet. In 30 years the house will probably be worth nothing.

During the term, the then vacant residential unit is to be rented out.

Which residential unit is supposed to become vacant?

The rent, we assume about 800€ warm, is to be saved half

Warm rent... always use cold rent for calculations! Consumption costs are deducted for the washing machine.

We are aware that we don’t earn much. Maybe everything is totally pie in the sky. How do you assess our situation? Is it doable?

Way too much credit, my opinion. There are more modest people who earn more.

The two siblings bring in the property and have the responsibility with the loan.

Which loan? I don’t see any loan here.