> If you do not have a mandate to govern from the people, you need unanimity from all homeowners. Those are the alternatives.

You don't strictly need a mandate from the people; authoritarian governments can be legitimate despite not having such a mandate. However, it's an impossible trilemma: successful action needs at least one of unanimity (parent commenter's approach), threat of coercion (government), or tolerance of free-riding (charity).

Can AI help here? Asking seriously

There are plenty of other alternatives. Where do you think organized crime came from?