Honestly, I'm interested in knowing some of this too.

https://join-lemmy.org/docs/en/administration/administration.html says about 150GB RAM and negligible CPU usage.

I assume an instance with users subscribed to active communities requires meaningful storage, but I'm not clear the sizes we're talking about (what's data growth per/day been like for some of the larger communities).

EDIT: Likewise, I'd love to know if that 150GB RAM is fixed or whether that number grows with use.

I suspect that it depends on if you're accepting other users and or communities. If so, you'll have to be global mod and probably spend time sorting out mod reports etc.

If you're just setting up an instance for yourself, it's probably easier but you'll need an account somewhere else to discover communities and index them back to your instance.

I would love to hear the answer to this as well. I guess it’s heavily dependent on how many users you have and if they are uploading images or just text, or just lurking.

I think if you did not allow signups it would probably be extremely minimal.