I recommend staying at Mert's place. It's a wood based room that has everything you need in the small space. Clean when I arrived. Kitchen has all the necessary items, desk for working was bigger than expected, bed was comfortable, and still enough space to walk around the room or leave luggage inside. A/C is above the bed and there is a heater too. It's located in a part of Istanbul that's like a cute village with many markets and grocery stores, so you'll never have trouble finding fruit or items for the fridge to eat at home. Location also is quiet, you won't here a lot of noise coming from outside because it's away from main street and it's not as crowded as other parts of Istanbul.
Mert is very hospitable and always helped solve problems and answer questions immediately. I hope every airbnb host is like Mert.