Yes, buying pre-founded companies is/was also a thing here.

I think in Berlin there was quite a demand for that in the ~2017 crypto wave, where a lot of companies were being founded and at the same time notaries/district courts were backlogged and the normal founding process could take a few months.

I doubt there is as much demand for it right now. I just founded a GmbH and the full process took 4 weeks (of that 1 day of active work). It would have been 2 weeks if I hadn't missed a letter regarding application fees, and it also helped a lot that I was flexible regarding notary appointments.

So with all of that, there is little value in using a pre-founded company, especially since you will very likely need a notary appointment anyways (for ownership transfer and/or adjusting the bylaws).

There are some gotchas, like how it can take a while (8 weeks for me last year) to get your tax number, and some (or perhaps most/all?) banks don't issue a credit card if your business account hasn't existed for at least six months or something. I can see how a startup not short on cash but in a hurry to start buying/selling could benefit from taking an existing company over.

Are you telling me that in Germany it's a viable business model to make a business creating and selling businesses?