Excellent apartment! We stayed one month at Esra's place. It was perfect! The flat has everything you can need during a short or long stay. It is very big, including the kitchen that is like another room. It has lots of windows and natural light (for me this is super important).
Location is good, in a lively neighborhood : you have a metro station close to the house (5-8 min walking) and a bus station (Shishane) with buses that takes you everywhere.
Near the house you'll find supermarkets (2 "Sok", 1 "Carrefour" and 1 local grocery store 100 mt from the house with nice people to help you).
Also it is close to Galata Tower (one of the main attractions of Istanbul) and the Istiklal Avenue (full of shops, restaurants, bars and the cute tram).
We stayed during January (winter) and the apartment had enough heaters to be warm. We loved the heater for towels in the bathroom.
Good water pressure and temperature.
Wifi worked good.
And also, we appreciated all the amenities that Esra have: shampoo, soap, clothing soap, oil, tea, coffee, kitchen elements, lots of towels, etc.
Keep in mind that the building itself is old and not well manteined (so don't be afraid when you enter), but Esra's apartment is lovingly taken care of and beautiful.
We'll recommend it and we would chose it again.