However, sometimes they met by the riverside.
Acts 16:11-15 11 So, setting sail from Troas, we made a direct voyage to Samothrace, and the following day to Neapolis, 12 and from there to Philippi, which is a leading city of the district of Macedonia and a Roman colony. We remained in this city some days. 13 And on the Sabbath day we went outside the gate to the riverside, where we supposed there was a place of prayer, and we sat down and spoke to the women who had come together. 14 One who heard us was a woman named Lydia, from the city of Thyatira, a seller of purple goods, who was a worshiper of God. The Lord opened her heart to pay attention to what was said by Paul. 15 And after she was baptized, and her household as well, she urged us, saying, “If you have judged me to be faithful to the Lord, come to my house and stay.” And she prevailed upon us.
Or in houses.
Romans 16:5 Greet also the church in their house. Greet my beloved Epaenetus, who was the first convert to Christ in Asia.
1 Corinthians 16:19 The churches of Asia send you greetings. Aquila and Prisca, together with the church in their house, send you hearty greetings in the Lord.
Colossians 4:15 Give my greetings to the brothers at Laodicea, and to Nympha and the church in her house.
Philemon 1:1-3 Paul, a prisoner for Christ Jesus, and Timothy our brother, To Philemon our beloved fellow worker and Apphia our sister and Archippus our fellow soldier, and the church in your house: Grace to you and peace from God our Father and the Lord Jesus Christ.
And look at how house churches are disparaged these days.