Someone wants their FB group to start earning from ads. How can it be done?
Since you mentioned that it's a health theme group
It's a health-themed type of group.
Then, create educational reels or posts about health-related topics; you can offer your group members to subscribe to your content.
A Subscription is a feature which allows you access to premium content on Facebook. You can use Subscriptions to support some creators on Facebook by paying a monthly subscription fee. This subscription fee gives you access to exclusive content and other items, such as a badge, that identify you as a subscriber.
https://www.facebook.com/help/219372401985734Affiliate is also good, but don't just post your affiliate links. Create content that revolves around that product, you know on social media content is king.