Stop looking and book this place NOW. You will not find a better location or host in Istanbul!! We were lucky enough to stumble upon this place and booked it for a 2-week visit with my girlfriend and her family.
The apartment is spacious, stylish, clean, and has everything you need for cooking meals and day to day living. My GF and her family are Persian and love to cook...her mom was able to make amazing meals as the kitchen had everything possible one would need to cook big meals...very rare in an AirBnB.
Now let me talk about the neighborhood. Simply put, Nisantasi is the most desirable neighborhood in all Istanbul and reminded me of the middle eastern version of Russian Hill in San Francisco...it's a place where many of the wealthiest of it's citizens live. Every block offers multiple bakeries, coffee shops, bars, restaurants, markets, etc.
We spent many of our days just wandering around the neighborhood and found it had everything we needed...we did not need to go anywhere. The only downside was parking is a bit tricky and we had rented a car for the entire visit (a must in my opinion). But there was a car park less than a block away that only charged me $100 USD for 12 days of parking with in and out privileges.
To summarize, I think you would be hard-pressed to find a better location, neighborhood, apartment, and host. Eren went out of his way to make us feel welcome and was super responsive to every communication. Thank you, Eren!!