Distinct legal existence:
This is a distinct legal entity, such as an LLC. Your "church" will need a governing body to run the legal entity it's formed under. However you decide to do this, it must be spelled out clearly in filing forms. There are a lot of ways to "govern" a community, and, since diversity allows evolution, I'm not going to describe any of them.
Basically, all you need is *some* legal incorporation. This is important for the legal aspect (if you are trying to subvert the legal framework within the legal framework). You will need this in order to own bank accounts and property collectively, and you may need this to remove or reduce the influence of the dominant system on your collective governance of finances and property.
If you, on the other hand, just have a communal squat that operates economically entirely in black markets then I don't know why you're reading this.
(Fun fact, which I'm skipping to because I don't want to forget it: As I understand it, The Church of the Subgenious skipped a lot of this by including "paying taxes" in their definition of their church. They pay their taxes every year, and the IRS rejects their payment, which proves they're a church. OK, back to what I was talking about...)
Edit: One thing I forgot about this. There must be *at least 3 /unrelated/ people* named on the legal documents. That is the minimum number to be a legal church.