Both Hani-ha and Hasim are slaves, but the nature of their indenture is different. Hani-ha was born the child of slave and therefore his is hereditary, although his mistress Lady Naballa has agreed to to release him if her serves her loyally for twenty years.
Hasim's situation is different. He was born a freeman, heck his brother is now a minor noble in the palace, who has agreed to a contract of servitude for a specific length of time and terms of conditions. In return he is provided room, board, and various taxes he'd need to pay are covered that would usually have to come out his pocket if he was a freeman prostitute. He is not paid for his services but is allowed to keep any tips he gets. If at some point he wished to void his contract he could buy out the remaining balance plus penalities. It is system that was practiced at different time in history.