Shopify has three different account types as well as standalone third-party products like themes and apps. Commissions are paid for sales of any of these products, including users who sign up for a 14-day free trial and then convert to a paid account. Shopify also has a wide range of blog posts, webinars, and video tutorials that can be linked to with the standard commission paid on any sales that are generated.
These ways of making extra money cover a wide range in terms of compensation and prestige. Check out the options to see what could work for you, keeping tabs on a projected per-hour rate so you can see what would be worth your time. The list is loosely arranged by 1. jobs requiring more skill or expertise, 2. gigs needing less and 3. things you can sell. And if you think of any good options I missed, please let me know in the comments.