Putting a hard rule on your community to join

Many communities realize that it's not wise to just let anyone in, but rather to restrict who can come in based on certain rules.

This company, the Consumer Club, has a rule that you must be $1M ARR to join. 

Hampton has a rule that you must have sold a business for at least $3M or make $1M a year to join. 

EO has a rule that you must have sold a business for at least $30M in order to join. These rules create a natural filter that creates a good community.