House construction. Sell or rent out the condominium?

Are there other solutions where the payment is max 1800€

Sell the apartment or build muuuuch smaller.

Kati, but you also have savings. You would have to deduct that first. And since the apartment is no longer heavily encumbered, there should actually be something left. You have to play around a bit with the numbers here. The claim that "many high earners alone have 5,500 net per month" I consider utter nonsense, corresponds to more than 10,000 gross per month.

There are two variants (with completely made-up numbers!!):
- Sell and a rate of €1500 with a family income of €5500
- Keep and a rate of €2500 with a family income of €6500 including rental income.

I was too lazy to use your specific numbers sensibly, but you see the direction it goes. With specific numbers and concrete interest rates for all loans, taxes, reserves, etc., it of course becomes complicated.
Sure, if you don't feel like calculating all the details now, the solution is simple: Sell.

One has to play around with the numbers here a bit. The claim that "many high earners already have 5,500 net per month alone" I consider complete nonsense, corresponds to a gross > 10,000 per month.

Well, there will be those too. But certainly they do not make up the large majority and presumably these people do not plan to build a towel plot in some remote village for an extremely high price. Those are perhaps the households in the top 3% - 5% of the distribution.

Nevertheless, the provocative previous post is correct – from a certain price level, without significant external money inflows such as gifts & inheritances, even "real" high earners are out. And when in a metropolitan area even double-income civil servants like teachers can no longer buy a house in the countryside, it will eventually get interesting.

There are two variants (with completely made-up numbers!!): - Sell and have a rate of €1500 with a family income of €5500 - Keep and have a rate of €2500 with a family income of €6500 including rental income. ... Of course, if you don't feel like calculating everything in detail now, the solution is simple: Sell.

The question is much more – do you want to cash in your apartment during a high-price phase and indulge in the currently very expensive "consumption" with the proceeds – meaning building a house – or do you want to become a landlord on the side in an entrepreneurial way – and even use this to finance your own home?

Since purchase prices are decoupled from rents, selling is probably more worthwhile than renting out. You state the cold rent at €900 – so 35 years of rent payments are needed until the purchase price of €380,000 mentioned is compensated. The apartment would then be almost half a century old. At the same time, you need capital to realize your house project. Both are significantly riskier. Since you don't plan to work full-time within the next 10 years, meaning you prefer money over time not, the rental variant sounds rather inappropriate to me. It's more work and risk.

Does €900 cold rent fit an apartment value of €380,000? As mentioned, if you back this up with numbers yourself, the above ratio should lead to a (clear) result. But then it has to be questioned again whether the €380,000 is actually achievable on the market at all, or whether the cold rent was set too low. Or both, because simple facts are out.