Heritable lease property the only solution?

Why should the lessor sell that? If I had plots of land, I would either build on them myself and rent them out or lease them under a hereditary building right (if I lacked the money to build). If you take the aforementioned 4-5% return and an increase in rent according to inflation or the standard land value (which should be roughly the same in the long term), then that is a great deal for the lessor without any real risk. If the lessee doesn’t pay, you even get a third of a house as a gift. Especially for foundations, this is perfect, as they can take money every year for their foundation’s purpose without touching the principal. Economically, it makes no sense to sell at all.

Why does the railway sell buildings and land? Who knows if the institution/church will still exist in this form in 30 years? Even large energy companies have partially sold their leasehold properties. Again: Who knows what will happen in 20, 30 years. Just because it doesn't seem economical to you doesn't mean the possibility doesn't exist.

We are currently building on a property with a leasehold from an archdiocese. Now brace yourselves, we pay almost €900 per month. Actually usury. The point is, there is nothing else. But we really want to expand. It is one of the most sought-after/expensive areas in the city. So actually, we are even lucky. There are no alternatives. If then existing buildings with oil heating from the 80s starting at €750,000 upwards, and that in completely different districts. Since we can finance the construction entirely from the proceeds of the sale of our current property, we like to sugarcoat the leasehold as "rent." So far, we have paid significantly more monthly for our condominium. The concerns that you are not the owner, I consider to be unfounded by the way. For a reversion to occur, a lot would have to happen. Apart from that, we can do whatever we want with the house and land.

we have actually already decided on the plot..

Cross out the word actually, then I congratulate you on a good decision - look forward to your bungalow. You are welcome to discuss the planning and later photos here :)

In retirement, a man still has monthly fixed costs... when selling you don’t get the plot value...

You want to enjoy the next 30 years now... then do it.

the second is the problem my kinds

Your children are probably not the problem. If you mean inheritance: as already said: you build for yourself, for you all... the children can and may acquire something on their own.

Now hold on, we pay almost €900 per month. Actually usury.

Fits with a land value of €180k (at least as of a few years ago, today up to €270k). How do you assess the value?

You, honestly. We've never really examined it this way before. We just thought, there's no alternative and is it manageable? Then we decided. The notary said something about nearly a million for the property and that it was totally overpriced. But I didn't remember that. We could only decide yes or no. Here (in our city) it's only about how much someone is willing to pay. There are many people here who earn a hell of a lot of money. My wife's boss, for example, about 30K € per month. Prices are based on that. A good example for the housing market in Germany.