This was my first time renting an Airbnb so I don't really have a benchmark to compare with other hosts/places. My wife and I stayed for 3 days on our short transit stop in Istanbul. Mehmet's place is a small building with 4 apartments that are used primarily for Airbnb. Mehmet has an office in the building and is often present there during the day. He responds very quickly and helps with anything you might need.
The building has a very narrow staircase so if you have many/big luggage items like we did, keep in mind that it's hard getting them up/downstairs (our apartment was 3 flights up). The place is about a 7 min downhill walk from main Sultanahmet square and about 7 min from the beautiful seaside (you should definitely go see the sunrise there). It's really ideally located to explore Istanbul, since the main historical attractions are all closeby. The apartment was very clean, exactly as described, and everything worked just fine.
Mehmet kindly came to Sultanahmet square to help us with our luggage (we got there by Havist bus), which was beyond what one can reasonably expect from a host, and which I'm thankful for. He also met us on our way out and helped us put our luggage into the taxi.
There are tons of similar B&Bs and small hotels/hostels in this area, so my only concern, if any, is that you could probably find something for a similar price in a 3* hotel with breakfast included. That said, Mehmet is a great host and this is a great little apartment, so I can recommend it.