Can I set it up so that users become affiliates after purchasing specific courses?

Yes, it's possible.You can set it up so that users become affiliates after purchasing specific courses.Follow the steps as shown below:

Desktop management console: On the [Recruitment Rule Configuration] page of the Affiliates section, select [Conditional] in the [Joining Conditions] field. You can choose to allow users to become affiliates after purchasing specific products, with a maximum of 20 products supported. Users only need to purchase one of these products to meet the application requirements.

Online Store: When users enter the affiliate recruitment page, an entrance to purchase specific products will be displayed at the top of the page. If users do not meet the requirements, they can enter the list page of specific products to make a purchase. If users have already met the requirements, they can apply to become affiliates.