Istanbul is a great city, no doubt about that. very nice and cozy.
about the apartment, it's a bit far from the old city, not far from the metro bus, however if you are renting a car, it's gonna be very busy on the roads 24/7.
Anyway, the apartment is nice and big and clean, have all the needed facilities, Abdelrahman is a very nice host who will help you with all the means. a very trust worthy guy.
I have to say the beds are not very comfort. but overall. the place is so beautiful and big and also very good with the money asked for it.
last thing, if you rent a car and you are going there, if your google maps is not working good, ten choose Esenyurt as a city to go to, not istanbul, and point your destination to the nearest biggest street to the apartment, because the maps in Istanbul is crazy.