Apparently the simplified serf and Lord dichotomy didn't stay the same throughout the middle ages, but developed. In the high middle ages the serf was bonded to the lord full stop but as we get to the late middle ages apparently it apparently became something of a social contract between the lord and peasant/serf, that could be negotiated.
Here is the link. Dude, just uhh, use libgen.is — at least for the anglo literature it is vast and very accomodating. I use other sources for literature in my language, but libgen should suffice for most things.
Also archive.org is great for searching things from last past century, old books et cettera.
I find it interesting that ancient societies ran on debt allocation, so much so that debt abolition was an actually platform politicians would campaign on.