How reporting royalty income affects taxes for authors

It is well established that an author who is engaged in the business of writing for income should report royalty income on Schedule C, not Schedule E. But what about a retired author who no longer is writing but still receives royalties from previous work? Should retired authors report royalty income on Schedule C or E? Or, should a sole-proprietor S corporation that reports royalty income as corporation profits and author wages be used? Each reporting method has tax consequences and legal issues.