This apartment is great for big groups. My family and I (group of 10 adults and a child) had a great time in there. Garen is a super helpful and nice guy. Unfortunately he was on a business trip when we arrived but his parents were lovely and really helpful. Two points to bare in mind: 1- Google map can give you the wrong address and take you to the wrong location. I would recommend asking Garen for a written Turkish direction or an audio note describing the direction. I recorded Garen's father's voice and played it for the taxi drivers. 2- the street and building exterior can put you off (special note to sole travellers)! But try and stay positive. The interior is great plus you can easily access the main areas of Istanbul with no problem. So although it might look not to your standard, it is a super convenient location.
I must say having such nice and accommodating people as our hosts made our stay much more pleasant. Looking forward to going back to Garen's place.