Honestly, I think the #1 problem to be concerned about right now is that there a lot of people self-hosting for the very first time, that maybe don’t really have much experience with hosting or moderation. It’s tough! There can be a lot of drama, random software failures, lost data, and disappointments that can happen. An instance can go under at random, at any time.
It sounds bad. In practice, the day-to-day can be fairly smooth sailing. A lot of people just kind of need the experience, need to make sure they’re not the one person moderating thousands of people on a serer. Making sure that moderation is a community effort, that the server has backups, and that there are channels for donations to support the instance - those things go a long way towards long-term stability.