Dumb starter question

But here the question: is it something to be done manually or is there a way for them to subscribe and open their blogs without my manual input?

After the initial setup, users can signup and create their accounts and/or blogs without your input. Also, it’s possible to allow your users to even use their own domain name (if you want).

But your users are still going to need help, and you’ll have to support them anyway. So it’s not totally hands-off in that sense — you certainly don’t have to create accounts for each user yourself.

Also, please note that while it’s definitely not quite rocket surgery, running a WordPress multisite network requires a higher level of technical know-how that running a standard WordPress site.

Here are some official support articles to get you started:

Before You Create A Network

Create A Network

Multisite Network Administration