That was the title of an info product (on CD) by a friend of mine from over 20 years ago, named Yanik Silver.
You don't need that CD to understand the concept:
There are thousands (probably millions) of books and other publications that are now in the public domain! Which means...the copyrights have expired and they can be used (by anyone) in pretty much any way they want. Such as re-publishing. Or editing into a new version. Or a version with YOUR insights and commentary.
So you're thinking "Yeah, but OLD stuff is old and not interesting to people today."
THINK AGAIN!
Sure, some books are outdated and have no real use today, but...there are so many that ARE or COULD BE useful today, that it boggles the mind when you look into it.
It really IS a GOLDMINE. (even if you don't have Yanik's CD and course on the topic).
Q: How hard is it...to get rights to books and other works in the public domain?
A: You already have the rights to these assets...NO NEGOTIATION NECESSARY!!!!
Oh yeah, did I mention how EASY it is to us A.I. to research and re-purpose and re-write public domain works?
""Even truth needs to be clad in new garments if it is to appeal to a new age." - Georg C. Lichtenberg