Voluntary slavery here, means that the ultimate control of your own life includes the right to give it away, sell it, or end it.

It does not mean chattel slavery, or involuntary servitude, or even involuntary government seizures.

And your point is? That it is okay to demand that poor people agree to become slaves in exchange for access to health care for their family?

No- that private property rights are consistent with the libertarian quote above because it's voluntary.

You can argue what truly voluntarily slavery would look like in a modern world, but involuntary chattel slavery is what conflicts with principles of private property.

I'd argue things like athletes signing away future percentages of potential earnings (which was a fairly popular idea until the current NCAA name and likeness rules changed) would be one potential version.

Too late to edit: this is published on Lew Rockwell's website, but the author of this article is Walter E. Block.