We loved staying in Yusuf's airbnb! Yusuf and his staff were incredibly hospitable and friendly. The airbnb was spacious, clean, and quite the deal. There's a turkish bath and sauna in the basement and a jacuzzi tub in the room. It's definitely in walking distance to many of the sights to see in Sultanahmet. They also have some tours they can arrange for you that were pretty affordable.
Please note this space is not a traditional airbnb (i.e. someone's home), it is more of a hotel. It's very affordable though and the Turkish hospitality is wonderful!