I booked Alper's place for two weeks for my parents and parents-in low, and in one word, my parents enjoyed every minute of their stay in this apartment.
What you can expect from Alper and his team member Enes is beyond a professional service, it is an authentic hospitality that make you feel like a family member, a friend, a relative or an old pal. My parents found the place clean, exactly the same as you see in the photos . Enes is there to resolve your issues, answer you questions and help you find other services you might need.
And the location, well, I had the chance myself to stay in Sisli. It is an authentic local neighbourhood, or as Turkish people call Mahalle. You will enjoy a convenient access to every popular/touristic destination, but further, have a chance to catch up with amazing local people, get connected to your local bakery, sit at a local pastry or restaurant and taste real delicious local food , not that of touristic ones.
Although the location is not by the water, you get a lot of chance to hear the seaguls singing at your roof and might have a chance to catch a stork's nest or say hi to a street queen ( i.e. the most amazing creatures, Istanbul street cats) while taking your Turkish coffee in a local cafe.
So, if you are looking for experiencing a real Turkish hospitality, I definitely suggest this place, and these people.