The very first location I can think of is a prison parking. You can see a lot of cars there and if there is no Sultan, just drive away far enough, turn around and come back - cars will randomly spawn and eventually you will get your Sultan.
As I mentioned, it is much more likely that you will get Sultan there at first time and if something will go wrong, for example, a cop or a guard will shot you, Sultan is not going to appear there for a long time. Or maybe I was so unlucky.