A few points about local FB groups and building your service business:
1. Remember that it isn't your personal page. I see a lot of cringeworthy posts from cleaners about personal matters, disputes with neighbors, family, local authorities, etc. This sort of thing can be very damaging to your reputation.
2. Don't engage in disputes or passive/aggressive cryptic statements about experiences with customers that you may have in the area.
3. While it should be obvious, resist making comments about politics, or personal views about most anything.
4. On a more positive note: Make posts supporting other local businesses, positive community events, and volunteer yourself in doing things that support/improve your community. Just dropping ads on the page won't help you nearly as much as you being perceived as a contributing member of the community.