Me and my girlfriend stayed at Tayfun's place for 18 days. It is quite a long time, and we were looking for a place that could feel more like a home than a hotel room, and we really liked what we got.
Tayfun was quick in responses and provided all the information we asked for. His family members live in the same house just below the flat - they met me and gave me the keys, as well as showed me the flat. Tayfun's aunt many times offered us tasty home-made pastry and other food - she's super nice and welcoming!
The flat itself has 2 rooms: one bedroom with a big bed, and a living room with 2 sofas, table and a chair. It also has a kitchen, equipped with all you need to cook, including pots and pans - as well as gas stove and fridge. You can use washing machine, iron, hairdryer and many other small things that are very appreciated when you're away from home and you can't carry everything with you. But the most exciting thing about this flat is the balcony - the view is just amazing! It is really just like the photos, and even better! You can see the Golden Horn bay, the New Mosque (Yeni Camii) and Suleymans Mosque (Suleymanie Camii) just from your flat - and when the weather is nice, you can have your meals or enjoy some tea with this view.
The location is also very nice - you can walk to Taksim square in 15-20 minutes, and Istiklal street is just some 5 minutes away by foot. There're a few bus stops nearby, and using the buses you can easily reach the Sultanahmet district or any other part of the city you may be interested in. There're also a few small shops just across the house, and a few minimarkets on the street - there you can buy fresh fruits and vegetables, and other food too. At the beginning of the street, there's also a kebab place with tasty food and reasonable prices - more of them can be found on the neighbouring Omer Hayam street. The neighbourhood is quite hilly - on the way to the flat you'll go down, but every time you go out you'll have to climp up. You should consider this if you have some complications with walking or you're not a big fan of it - but the whole city is like this and you won't be able to avoid it anywhere in Istanbul. Just in front of the house, there's a mosque, and bedroom windows look just at it, so get ready to wake up with the first morning prayer - but for us it wasn't a big deal, and on the 4th day we stopped noticing it and didn't even wake up because of it.
So, this place was perfect for us, and we would definitely come back and stay here next time we visit Istanbul. Tayfun and his family are very welcoming and helpful the flat itself is nice, the balcony view is something you could only get in 5-stars hotel, the neighborhood has everything you may need and it's really close to main touristic attractions. 11/10, you won't regret staying here