I can give you an example. I had occasion to dig through some of the Oliver Pollock papers some years back, at the Library of Congress. He was a New Orleans merchant, originally Irish, whose excellent connections with Cuba enabled him to become also a slave dealer- as most slaves in this period would come through the Caribbean. There were a few letters in 1775 from a James Ramsey or Rumsey, who was likely a merchant operating in the Northwest around what's now Michigan. Ramsey needed his slaves only intermittently, and had placed them with Pollock to be hired out while he was away. Pollock rented them to someone who'd used them very badly, and Ramsey was furious: mentioned that one, a boy, "now has a broken leg". The implication was, of course, that like any rented tool today, slaves rented in this way back then could be expected to be used very roughly, unless there was some sort of contractual oversight- in this case, Pollock had asked for no such thing and Ramsey was angry at how his property was now damaged. The rent was six hundred dollars ( almost certainly Spanish dollars) , which Ramsey felt Pollock was responsible for, and he clearly intended Pollock to pay damages for the boy with a broken leg. How the matter concluded is unknown. Pollock would go down in US history as one of the financiers of the American Revolution- which broke his business. The slave trading has gotten less attention.