Darius hired special rank adventurers, they were children who wanted to be adventurers, but because they were weak or didn't have a group and age, they ended up taking jobs that most adventurers would refuse, such as shopping for someone, sweeping, or making food. Household chores that were within the city walls and involved no or minimal danger, they were easy jobs to perform and therefore paid little.
Poor children accepted without complaint, even adults in some cases. It was cheaper than going to the Merchants' Guild and being put on the list of someone who wanted a job.
In this case, each job was counted and when they wanted to they could accept a promotion in rank or continue in the same one and keep those missions.