After having purchased all the slaves who would serve as workers, Andrew did the same when he opened Dunnas Palace and brought several of his employees from Cannaris Palace.
The employees of the Cannaris Palace were his oldest employees and therefore the most experienced. Furthermore, in this way, the new slaves could ask them questions and have a better understanding of their situation.
The courtesans had already asked Sonia about the treatment they would receive and so on, but the other slaves did not. Although they were clear about the work they had to do, which did not entail any risk, they were still unsure of the treatment they would receive from Andrew.
Since the employees of the Cannaris Palace are on the same level as these new slaves, at least in the minds of these slaves, they can be more direct and ask their questions.