This depends on their need for money. There are no county, state or national 4-H dues. If a club wants money for some activities, it usually charges dues or conducts money-making activities. The 4-H department also asks for a simple financial statement at the end of the calendar year. Any place large enough that is convenient for the members of the group.
Some clubs meet in leader's or member's homes or garages.
Some meet in a central place such as a school, church or community room. This depends on the age of the members, the place they have to meet and the leadership available. The ideal club is big enough to have fun and learn together, but small enough for everybody to feel a part of the group. An adult who works voluntarily with a group of 4-H members. Yes, some adults teach members to do things.