Facilities are the available kinds of gyms available in the shop. These facilities are important to upgrade over time, as the starting upgrades are relatively inexpensive but give improvements to, maximum members & prestige, different tiers of equipment and roster size, unto a cap of 15. larger facilities will also be able to hold more equipment and get more prestige from daily collection.
Members pay to come to your gym to train and hang out with the fighters.
You do not find basic members in your Roster.
Members seek to find the most prestigious gyms.
Therefore Members are attracted to Prestige.
The more Prestige the more they like your gym, and if they like your gym,you gain more members.
Every gym facility has a max member count. The more members the more money you get, collect the stash with cash whenever its full or you will miss out on potential income from the members.