WHERE and HOW do companies like VideoBox.com and VideoZ.com
(downloadable adult movies) get all of thier video content from? 

Also, how do they get the licensing or distribution rights to let an
UNLIMITED number of people download an UNLIMITED number of movies to
thier computers (which they can then view forever) for only a simple
(and very CHEAP) monthly price?  Is there a master studio agency that
is selling them all the movies and rights in bulk, or do they have to
go from studio to studio and individually negotiate new contracts with
each one?

I am looking to get into the same business (with my own fresh spin on
the concept) and need a few places to start.  I also noticed that the
mojority of the movies are all THE SAME TITLES from one website to
another, leading me to beleive that they are all going to the same
sources for thier content.

I believe they use Adult Platform's affiliate program (VideoBox.com
links directly to their site via a "Webmasters" link on the bottom of
their pages)

http://www.adultplatform.com/wmfaq.jtp

That was where I started, and every site like them has a similar link.
 But their "Affiliate Program" is for other adult portal websites to
link BACK to the original site in hopes that the user will signup and
they will get a commission.