So I've been looking at other POD sites like Teespring and Teepublic that let designers create an account, upload their designs, and make a commission from sales of their designs. They would also need to be able to track the sales they make. Is there a way I can set this up for my Shopify store? I'm not sure what this is called (kind of like affiliate marketing without the marketing part)
Karlie here from the Shopify Guru Team! I've taken a look at your post and I have some apps in mind that could help you with the functionality you're looking for.
What I would suggest you do is use an app like, Teelaunch or Printful to create apparel and then I would suggest using an app that would allow you to have multiple sellers to create products and collect commission. Specifically, I would recommend looking into the apps:
As for sales, you could simply use the reporting feature from your Shopify Admin. To access the reporting features available to you, you would head into your Shopify Admin> Anayltics section. Using our guide would be a great resource to help you navigate through your reports and storefront analytics.
I hope this helps, but if you have any further questions - be sure to ask and I would be happy to help!