We had a lovely one week stay at Afranur's flat. It is very conveniently located, near a T1 tram stop, at a walking distance from Karakoy port, and access to most places in the city is easy. There are a few coffeeshops and supermarkets around which bring you anything you need.
The flat in itself is very clean and comfy, it has everything you need. It is a very good price-quality ratio. We were at first pretty surprised by the access to the flat, but then quickly found out the area is pretty calm and we felt safe there.
We had no problems for checking in and out, Afranur's directions were very clear and he was quick to reply to our messages.
We would recommend staying at Afranur's place if you plan on visiting Istanbul