"Royalty checks" refers to payments received by someone, usually an artist or author, for the use of their creative work. It is like getting a small piece of money as a thank you when other people or companies use what you created. Full definition
Or until you sell through, which means you have to pay that advance back and then you'll start getting royalty checks. (thecreativepenn.com)
After a book earns out, the author receives royalty checks on a regular basis as long as the book is in print and still selling. (thebalancecareers.com)
Published authors might recognize their debut release, first royalty check, reaching a bestseller list, etc.. (jamigold.com)