Sell a new building and buy an existing property - pitfalls?

And then you don’t yet have a reserve for the valuation discount for the 100k. In other words, the bank is financing at full risk

Or put differently – not financing at all. So if the lending value from the bank’s perspective doesn’t match, financing quickly falls through.

(...) We also had people during the sale of our house who could show us their account balance and simply had the required money lying around in cash. So there are such solvent buyers as well. (...)

But they only buy in prime or at least promising locations.
Because for this clientele, buying real estate is comparable to when the average person buys 2 shares of Tesla.

Munich Schwabing, Erlangen Tennenlohe, Hamburg Blankenese. That works, even with old buildings.
But in Berlin Neukölln, Duisburg or Hanover Vahrenheide... even a new building has a hard time, an old building becomes unsellable...

Location, location, location, location... and since the energy crisis also:
Heat demand, heat demand, heat demand, heat demand...

I honestly can't imagine that any bank would go along with this "lazy" swap of old for new given the "low" salary. Mathematically, you can't service a (new) loan if living expenses are taken into account.

We have just done exactly that, or rather are currently in the process. We have signed a contract for interim financing as well as a contract for the exchange of securities for our old loan. What hits hard at the moment is the interim financing, which usually lies about 1% above the interest rate of long-term loans and, yes, also has to be closed for the entire or almost the entire purchase price by the questioner.

The new credit framework guideline specifies that the interim financing must not be higher than the expected sales proceeds including the usual discounts of the bank. For us, for example, it turned out that the bank’s real estate department (and also two realtors in our town) expect sales proceeds of about 500k, but the interim financing can only be concluded for 400k... at just under 5% interest. In addition, there are nearly 2k in costs for the exchange. Additional costs beyond that for the purchase as well as incidental building costs must be financed through equity.

The goal for this project should therefore be: buy the property with handover/payment of purchase price, for example, only in 4-6 months after signing, quickly sell your own property, and have only a short period of interim financing, paying 50k+ in incidental costs.

The other loan conditions of the old loan remain unchanged with the same term.

They only buy in prime or at least promising locations. Because for this clientele, buying real estate is comparable to when the average person buys 2 shares of Tesla.

At that time, we sold in a rural area and had a purchase commitment from the people. They just wanted a house in that town, for themselves to live in, not necessarily as an investment.