The apartment's location is perfect if you want to discover the old city of Istanbul. Ozkan and his wife were very welcoming and helpful when we asked them whether it was possible to have a fan in the apartment due to the heat, they provided us with it very quickly.
Only note that this area is very difficult to access by car/taxi, using the public transportation system may be more adequate (tram station 5 minutes away and subway station at around the same distance).
The area is super safe as it is located next to the central police station of Istanbul, we never felt unsafe.
We definitely recommend you to stay there if you want to explore the old city.