Whatever his contract specifies. That's how a record label deals with an artist. They both sign a contract, the terms usually dictated by the label. If he is popular enough, he can ask for more money...
Here are the results of my research:
-- Interscope Records --
Interscope Records is not owned by a single person, but by Universal
Music Group. Originally founded by producer Jimmy Iovine...
The RIAA has a searchable database where you can look up what gold and platinum albums an artist has received. Note that his only reflects sales in the United States.
If you want to know about an...