Wow, I bought another C64 on eBay. There was basically zero description on the listing. It could be defective. But I should be able to sell it for that price. Otherwise it would be good for spare parts.
EUR 57,00 + 7,50 shipping
I was also looking into buying some used 5.25 floppy disks. They are not hard to get but are quite expensive for my taste. One of the cheaper offers from England:
I got it those for EUR 9,20 + 6,22 shipping:
And I soldered the cable for the C64 floppy drive today. And then connected the 1571. It reacted at LOAD “*”,8,1. But since I don’t have any floppies, I can’t test any further. The noise it made when I tried to load was quite a loud crackle. I hope this is not a bad omen.