In digital marketing schemes and especially in link schemes, the term "money site" refers to the website we want to promote. It is said money site as it is where money is finally earned.
The term money site is used to differentiate the latter from all other sites or pages which may have been created for SEO purpose - domain satellites for instance.
In link shemes, backlincks or first tier backlinks point to the money site.
A money site at the top of a link pyramid:
Image credit Royalteamseo.