I probably overstated in haste to reply. What I was trying to get at was indenture and similar arrangements. Like I said, I don't know enough about the specifics to offer guidance, which would probably vary greatly depending on circumstances. In the big picture what I think doesn't matter anyway. Not a gatekeeper, not trying to be don't want to be!
It is in our interest to be very diligent about differentiating slavery from systems of indenture. We're all familiar with the "Irish slavery" trope that has infected family history sites. It conflates indenture and slavery and is used specifically to downplay the impact of slavery in America and on Americans. I'm not saying anyone here is or would be doing that, just that it behooves us to draw a sharp line. That's not always easy or obvious - I can think of several examples I've seen where I'm just not sure.
(Another wrinkle - many slaves in the U. S. today are presented as indentured servants, but the conditions for their release - often repay a debt or such - are constantly moving just out of their reach. And yes, there are slaves in the U. S. - an estimated 400,000 in 2018.)