There are three VERY lucrative ways to make money with the Shopify company.
1. Design and sell themes
2. Design and sell apps
3. Sell stuff through their eCommerce platforms.
For the first two you have to sign up as an affiliate to gain access to the portal and all the API’s and training stuff you will need to make themes and apps.
To sell through your own store you can sign up here to get a 14 day free trial.
Go here if you want to read more about it and some of my experiences with Shopify.