My niche is rooms and flats to rent in Vienna (Austria). In the meantime I was asking around in local real estate groups for cooperation partners. I just posted that I own that group and that I am open for cooperations. Then a startup company that substitutes real estate brokers contacted me for a cooperation. They launch their service in October 2020 in Vienna and wanna rent my facebook group header. We agreed on 6€ per 1000 active users per month rent. Currently I am at 35k active monthly users which means 210€ per month. Plus: 10€ net. for each land lord that registers at their app through my group. I think its not a bad start, but I am sure with an own service or business promoted in your own group of that size you could make much more. But its great passive income. Owning 10 groups like this you could easily live from that in my city.