To be precise, not everyone can join (indeed it is the non-profit bylaws that establishes this) but to be tax exempt it has to be what is called "open". I.e an

To be precise, not everyone can join (indeed it is the non-profit bylaws that establishes this) but to be tax exempt it has to be what is called "open". I.e any person that fulfills the membership criteria can join (and it is the non-profit that decides on there should be a fee or not). To be a non-profit you also have to spend at least 80% of the income on the stated purpose of the non-profit (which of course might benefit members in the way that the goals of the non-profit is worked on but not in the way of paying money to member).