The apartment is quite new and it's nice. We were two and there are a double bed plus a single bed inside. The position is great in order to visit Sancta Sofia, Blue Mosque, Topkapi Palace, etc., even if the neighbourhood is dirty and dark at night. Although you can feel unsafe, nobody bothered us even late.
At a first glance the room seemed clean, but there was some hair around and in the bathroom. Anyway there is a vacuum cleaner outside the door you can use.
Mustafa is very kind and available for any information at any time.
Nearby you can find many services and I definitely recommend fish sandwich at a street vendor in Kadirga Park.