First of all: Kalen is probably one of the most friendly and proactive hosts I've ever met on Airbnb. When arriving he offered me a quick tour around the neighborhood and gave tips about what to eat and how to get to the local attractions. He is a great communicator and helped me out a lot.
The apartment is nicely located in a side road, so it is as quiet as a city like Istanbul can be. The main attractions are perfectly reachable by a maximum 30min walk.
The apartment itself is very simple. I do not really have a calibration on what to expect at this price tag in Istanbul, but unfortunately some of the details - e.g. a small stain on the bedside table, the linen on the bed that was clean, but definitely quite old, the mattress could be better, the shower head not being high enough for me (I am 185cm), a not properly attached power outlet - that made it a little bit uncomfortable. It was okay for my 2 nights stay, but I personally would invest a few lira more for my next visit.