A few hours before check-in, I was informed by the host that I had to provide copies of passport for all visitors. That was very stressful and the wording used by the host was not great either "do it within 12 hours or the booking will be cancelled". Surely this could have been communicated a few days before, or even just after the booking took place, to allow for me to coordinate with the other four parties to upload their details on the shared link.
Upon check-in, I realised the flat had not been cleaned. The beds looked used, there was no toilet paper, and no towels had been replaced. Someone came after me to clean and I was assured they would also bring toilet paper -which they did not. I then had to go buy toilet paper myself, the cost of which was thankfully reimbursed by the host.
The location is great. Kadıköy centre can be extremely busy and noisy, but the flat is located just out of the busy part of the district with nice cafés just around the corner and walkable to anywhere.