I don't want to retread the reason for it that others have gone into on why Biblical Churches were House Churches. Chuck Missler and Rob Skiba and others do a good Job of that though they also hold views I don't like. I do like to repeat that there were no Church Buildings till the third century.
For me this overlaps with my objections to the modern concept of a Pastor and why I object to 501c3 Churchs.
The Pastor I do not like to name did a sermon against the House Church Movement. He of course said a Church could meet in houses. His main issue was that he said The Church should grow and any successful Church should eventually become too big to fit into a house. When a Church becomes too big is when it should split up into smaller churches, every city had many churches in NT times as the NT shows, while still not being the majority population anywhere.
This same Pastor when he preached against Women Pastors, criticized certain Churches who will claim to agree with his view, but let a famous Woman in the Christian world speak while calling it a "Seminar" rather then a "Sermon". That is easy to mock because basically Sermons are Seminars.
Sermons are Biblical, Jesus did Sermons and so did Peter and Paul, and I believe the reason 1 John lacks the usual Epistle introduction is because it is really a transcript of a Sermon. I've grown Spiritually a lot from listening to Sermons and Seminars from believers I both agree and disagree with. But that's not what a Biblical Church is supposed to be.
If you look at the instructions given in Corinthians, a worship gathering is supposed to be multiple believers preaching and prophesying and testifying. It should be everyone edifying each other. It's not supposed to be one man giving a long speech while everyone else just nods in agreement.
A study of the History of the Synagogue will show that they also began as House Synagogues and buildings showed up later.
Critics of The New Testament love to attack The Gospels and Acts for referring to Synagogues because "the modern Synagogue didn't exist till the 2nd Century, after the Second Temple was Destroyed". The Emphasis is on modern, I don't know why they think the not very detailed NT descriptions imply it's Synagogues had any of the characteristics that started after 70 AD. I see no NT evidence any were ruled over by a single Rabbi. And I so no clear evidence that they weren't house Synagogues.
Josephus is proof the term Synagogue was used before 70 AD, and Archaeologists have identified plenty of Synagogue buildings that go back to Hasmonean times.
People who object to Rabbinic additions to Judaism may desire to object to the idea of Synagogues. But the Epistle of James does use it as a synonym for Christian Churches, but the KJV translated it Assembly, in Acts 13:43 the KJV translates it Congregation. There is also one place the NT uses the word commonly translated "church" to refer to something in the Old Testament,
Acts 7:38 used it to refer to the congregation in the wilderness in the days of Moses. Two Hebrew words are commonly translated Congregation in Exodus, Strongs number 5712 and Strongs number 4150. Both of them are also used in Psalm 74. That is the same Psalm that is the only place the word Synagogue gets used in English translations of the Hebrew Bible, including the KJV in verse 8, to translate Strongs number 4150, this same word is also used in verse 4 but translated Congregations there.
The Greek word translated Church comes in it's Secular origin from a term used to refer collectively to the entire citizenry of a city-state, that is the sense being drawn on for The Church, we're Citizens of the Kingdom of Heaven, but can also refer to any gathering together of Citizens, that is the local church.
Strongs number 4150 is also sometimes translated Feasts in Leviticus 23. It refers to times appointed for God's people to gather together. But only 3 of the Feasts required everyone to gather in Jerusalem (or wherever the Tabernacle was), the rest could be just a local gathering. Under the New Testament, The Church is The Temple, so even most Christians who think we're still under the Mosaic Law don't see Christians as being required to Pilgrimage to any certain location, (besides Catholics). And The Sabbath is an Appointed Time itself because it's discussed in verse 3 of Leviticus 23.
So that Synagogues also originally met in houses is further backing for the House Church position in my view.
This is also why I don't necessarily consider church buildings bad. Even mega churches can serve God. But what I am very suspicious of is any church that operates like it's a business. I believe if you have a building it should be legally the private property of a member of that church choosing to share it with the rest of the congregation.
A Biblical Church shouldn't need a 501c3 status, it should be taxation proof to begin with because no one is paid a salary and all money given are freely given gifts. I support abolishing the 501 tax exempt status period for both secular and religious institutions. A Church that behaves like a corporation should be taxed like one.