Affiliate Marketing Secrets

I’ve begun to write piano sheet music of Green Day song with Sibelius and upload them to the internet for free (which I have read is legal. If it is not please tell me.). I have the ability to make a small amount of money from this (from filesonic.com, affiliate marketing, and donations), but have thought about selling the music for a low price once I have a relatively large collection. How do I get a license for this and about how much are the royalties?