The situation was almost the same in the Classical world. The only difference being the debt relationship was personal and not institutional.

You can do whatever you want while you pay back loans today as long as you keep your contact information current. Just try and move without informing your lenders. That can be treated as a default. And if you can do whatever you want while maintaining a suitable income to make these sort of loan repayments, your experience is an outlier for all but a very small portion of Americans.

It was actually the same way. Outside of their slavery obligations, they were allowed to do whatever they wanted to pay back their sum to earn freedom, more or less. And of course, they did have their housing and food covered meanwhile.

I have to figure there were a few textile mills in cotton states that were operating before the Civil War using slave labor.

This could be run like a regular factory with bookkeeping techniques where labor cost was certainly not zero even though laborers were not getting paid nor free to do anything else but go back to picking cotton.

Labor cost could be reduced to a single line on a spreadsheet like any other business.

After the war with slaves now being paid and free to work elsewhere if they could manage it, this would be offset by the workers paying their own upkeep after the slaveowner had become the employer.

There would have been pressure to keep labor cost from escalating at all if possible.

So things could go forward with as little change in financial risk as could be.

A lot of companies today still have the same type structure as these places had after the war, which can be not much different than the structure they had before the war, and Wall Street is still in the same place it was before the war . . .

While the comparison here is not about chattel slavery of the type practiced in the US, if I remember correctly the amount/ratio of surplus value extracted from slaves and then emancipated workers was not actually all that different. There was a drop, but it wasn't that big.

A big part of that was the increased productivity of freed laborers being compensated by an increased cost of reproduction.

'outside of their slavery obligations' do some heavy lifting here. Slavery means something, and nothing can mitigate that.

There are many types of relations that were referred to as slavery throughout history. The common, vernacular English definition does refer to chattel slavery and there is an onus during discussion to make oneself clear.

Having said that, equating all slavery to chattel slavery and thus denying that other slavery-like arrangements have existed and continue to exist today is not only a misleadingly US-centric perspective, it also removes the ability to criticize and try to reform social arrangements that severely restrict freedom in subtler and more nuanced ways.

If we're talking about late ancient societies, slavery often meant social subordination to your master and some obligated work.

It is not dissimilar from undischargible debt. In fact, the historians and anthropologists writing about these societies have made the link themselves.