This is a note for the future guests. The house is about 14 minutes away from metro station Şişhane. The shuttle bus from Istanbul new airport (IST) stops at Taksim square (near Taksim metro station), which is about 18-minutes away on foot. I arrived after midnight but most of the shops along the way were still working.
The location is very good for exploiting the main attractions and for short stays.
There's a cat in the apartment.
There's a mosque near by, which means that you should expect to hear calls for morning prayers (you can check prayer time online). But with earphones I didn't hear most of the calls, even though I'm a light sleeper.
If you come out of the building then turn left, in 3 minutes you'll find a local cafeteria (the kind you might see in the universities) with cheap tasty food.
Ali did his best to make sure my stay was comfortable, for example, agreed not to smoke indoor.