Doruk is an amazing host. Responsive, courteous, and friendly. He communicates well in English, a much-needed skill if you are in Turkey.
As for the place, it is a two-floor duplex on the third floor. There is no elevator, so be mindful if going up the stairs is an issue. The place is clean, spacious (we were a family of three), and has all that you need to feel at home. It has utensils, toiletries, dishwasher, iron with board, washing machine, TV with cable, and, high-speed fibre optic internet. It has a nice balcony on the second floor and a working desk.
The location is in a good residential local neighbourhood, not touristy at all and not fancy. So, if you want to live among the Turks and not foreigners, then it's right for you. It's quiet, safe and clean. You are surrounded by plenty of super and mini markets for your daily groceries, as well as pharmacies (in case you need it). There is a nearby bus stop (3 mins walking) that can take you in 15 minutes to Osmanbey, where you will have access to the metro, the preferred mode of transportation to bypass the dreaded Istanbul's traffic. Given it's in Sisli, so it's a short distance to Cevahir mall and the nice neighbourhood of Nistansi.
We really enjoyed our stay at Doruk's house and would certainly recommend it to others.