The idea of slavery as a legitimate early stage in economic development is well-illustrated by the Biblical story of Jacob's two marriages:
"After Jacob had stayed with him a full month, Laban said to him:
'Should you serve me for nothing just because you are a relative of mine? Tell me what your wages should be.'
Because Jacob loved Rachel, he answered,
'I will serve you seven years for your younger daughter Rachel.'" (Gen 29:14-18)
Again, given such primitive level of division of labor, most "jobs" in those days were unskilled and paid equal subsistence wages. There was no advantage in being free.
But if you more-or-less enslave yourself to a master, as Jacob did to Laban, perhaps he'll let you marry his daughter 7 years later.