Two years ago I started a small Facebook group for productized service business owners, with no real objectives in mind: Just sharing insightful content and examples of productized services I found.
The group was pretty dead for about a year in a half but I started investing more time in it back in July 2019.
It took 1.5 years to get to 1000 members, and then only 6 more months to get to 2000 members (around January 2020).
Fast forward to today: The group is really active and has 2360 members. I've pre-sold our SaaS there (ManyRequests) and made about $15,000 in revenue doing that.
I'll write a case study about my learnings and how to build a Facebook community and how it can be beneficial for your product / service. Let me know what you'd be interested to learn :)
Here is the link of the group for those interested: https://www.facebook.com/groups/192719694795609/