Depends on your region, but let's not pretend it was some rarity pre cotton gin. You didn't need to be as rich as yo think to have slave labor.

Quite the leap to go from "pre-industrial people" to "Antebellum US Southerners", and even then the majority of that (hyperspecific) group did not own slaves.

If you include all pre-industrial people in history, then yes enslavement of outside groups is very much the norm not the exception.

Citation needed.