it is important to think over the payment system. any online game should be profitable. in the distant future when the game is completed for the mass player.
1) in-game store - endless items, resources, in-game money, boosters and more.
2) paid subscription - access to disposable items (one-time purchase), cosmetics, skins, VIP profile design, decorations for a character / weapon / item and more.
if the game is far from pure survival genre, then some income options can be applied. Or leave it single play (coop). no servers, no support, no costs.