Some churches own buildings. Some do not. The church of which I have been a member for the past decade owns a building which is too small for its congregation; it would like a larger building. The church of which I have just become a member does not own a building at all, and does not particularly aspire to own one; we might not take one if it were offered for free (although we might - if you have a building going free, let me know, and we'll see...)
It's all just irrelevant, right? Just a matter of preference and pragmatics. Certainly I've never really read anything discussing the theological or ecclesiological importance of church property (except in the Catechism of the Catholic Church, paras. 1179-1186; it is the usual quasi-sacramental stuff that characterises much Roman theology).
Except buildings become symbols, and symbols take on significance they may not have had in original intention. Because church buildings are not particularly gospel things, they are also not particularly controlled when it comes to their symbolism. Being a long way from the heart of the Christian faith and its practice, they can take on different meanings very easily; they are not tied closely to any particular interpretation of the faith. So a building could become a fortress; in here we are safe, in here it is holy, in here the world will not get us. Or it could become a temple; in here God is present, in here God is working, in here prayers are heard. Both of these would be very unhelpful symbolism.
I would guess that the most useful symbolism you could apply to a church building would be that of an embassy. An embassy is the sovereign soil of another country, and so in a way the church building, by dedicating a particular portion of the Earth to the service of God, becomes an embassy of heaven. It is a strange embassy in one sense, because part of its central message is that this ambassadorial role is temporary; there will come a day when all of the Earth will be similarly consecrated. As such, the church building can have a prophetic role. Like an embassy, it can also aim to display something of the kingdom it represents. Obviously that will mainly happen through the people who gather there, but it can also happen through the architecture, the liturgy, the sheer ambience of the place - and, given that we have a Servant King, perhaps also the regularity with which the building is available to others to use.
Of course people in the church will only think of the church building that way if the general culture of the church leans in that direction. It is easy for error to creep in here, and I wonder whether the way that church members think about their building might be a good indicator of how sound their grasp of the gospel is overall...
One thing I have seen a lot of recently is the idea that the church building is inherently detrimental to mission. If we have a building, people say, church members will start to feel disconnected from the wider community; they will start to think that evangelism just means inviting people in on to our territory and not going out on to theirs. Well, to this I can only say pish, and perhaps also tosh. It is true that people might start to feel that way, but it will not be the building that makes it happen; it will be the preaching and teaching, or lack thereof. Moreover, where do you think the congregation are for the 90% of their lives when they are not in the church building? They are scattered, hopefully being salt and light in all of the places God sends them. I'd also like to ask whether it might not work the other way around - whether lacking a church building might not symbolise a total lack of boundaries and distinction between the church and the world..? Mightn't it?
Some churches have a building. Some don't. It doesn't really matter, although there might be important reasons why at a particular moment in a church's life a building will be a huge blessing or a great liability. What really matters is what sort of symbol we allow it to become, and to what extent we see it in the light of the gospel.