Let me first start with a good thing. Yunus is indeed nice host and is quick to respond to your messages and was conducting our arrival nicely, being there to greet us in.
However, the state of the apartment you will see on photos at Airbnb are done long time ago. Once you get in, even it looks very comfortable at the website, it is bit smallish, and besides, there was one "alien" bed for additional person (which we haven't asked for) so I had smashed my toes several times trying to go between that one and main bed. Then several lamps/lights were not functioning. Bathroom has rotten plastic curtain at the bottom. It really looks disgusting. They should either change it or just repair the (I assume) previously existing glass door to it. The ceiling has a huge Mould and Brack around it.
The AC was not working at all. Anyhow, for this kind of price, I believe it should either be improved a lot, or offered with a significantly lesser price. As for my experience from renting quite a lot of Istanbul apartments in past 10 years, it will realistically have to be priced under 30 Euros (still without Mould and rot).
As for the location, it is popular area, though if you come with a car, it is impossible to park unless at the pay parking. And most definitely, you have to avoid leaving a car at the nearby pay parking, next to a mosque and petrol station, as they are a rip-off, charging at rates 5-6 bigger than any other parking just 10-15 minutes away. They have charger 300 TL for 24 hours keep (and also you leave your keys there, so they move it around with an increased risk of scratching it...and if you have a rent-a-car, no, you don't want to risk that). For example, there are few parking (even a closed one) spots next to Galata tower, which will charge you 60-80 TL for a 24h keep. And you need less that 15 minutes to get to the parking even it is a steep hill up from this apartment.