I have learned that if God chooses you to build a fellowship and someone else comes in with their own agenda, don't play Mr. Nice Guy. As I said I could write a book on what I learned.
The danger of Home churches not sponsored by a larger church umbrella are what you just described. Wolves can creep in and without oversight from elder deacons and the pastor...boom the group is lost and people scatterred and disillusioned.
So do you answer to an elder board/pastor to keep you from going astray with your two groups? It can be easy to go astray and not know it! You mention the agendas of others, which trusted counscellors keeps a watch on your agenda? I’m not accusing or insinuating anything. The early house churches were self sufficient but were still answerable to the visiting apostles and recognized leaders of the day and some received, when necessary, rebukes and admonishments to discontinue practises which grieved the Lord.