No file access after time limit and no join requests.
You could make access to the files after the time limit that they dont need to wait 10 hours to downlaod their world to maybe falix, godlike or aternos or install plugins. Without the world if you want to play you can't even use singleplayer or build the spawn or something. And you could add join requests that you can send them to friends and if they click them they join your server. If you say about the cost what if you use external drives and only one server that manages the files