I'd suspect the 'free' and 'no ads' would be somewhat mutually exclusive. Perhaps a particular group organizer pays a modest amount - $19/year(?) - to manage/moderate groups up to X000 members.
Which means it isn't free, it's a charity project paid for by the group organizer(s). That's probably fine in the short term, maybe even longer, but eventually the organizer(s) will move out of the area, or get tired of managing the group, or die, or whatever, and someone will need to manage it.
Honestly if it really would just need to cover the price of the cheapest hosting you can find and the domain registration a single small-to-medium Adsense ad in the sidebar might generate enough to cover it. I don't know how many impressions/pageviews it takes to generate $20 but it can't be that many.
Which means it isn't free, it's a charity project paid for by the group organizer(s). That's probably fine in the short term, maybe even longer, but eventually the organizer(s) will move out of the area, or get tired of managing the group, or die, or whatever, and someone will need to manage it.
Honestly if it really would just need to cover the price of the cheapest hosting you can find and the domain registration a single small-to-medium Adsense ad in the sidebar might generate enough to cover it. I don't know how many impressions/pageviews it takes to generate $20 but it can't be that many.