Ok, this might be a little personal and not much useful, but I am just curious, so bear with me.
Is a moderator's job a full-time paying one or is it more like a hobby, like for most other users?
If it is not a full time job, how come every question asked by every user on this site is reviewed and sometimes answered by them? How are they able to deal with that much traffic of closing/opening, answering, editing, questions on meta, perhaps some other SE sites and what not?
It's not anywhere near a full-time job. We only receive about a dozen flags for moderator attention daily. Most of them require very little of our time. A lot of our activity on the site is organic- we wouldn't have become moderators if we spent no time here, and we answer questions and review posts just like any other user would.
Stack Overflow aside, most Stack Exchange sites don't have that much traffic. Physics is currently the 6th largest in terms of questions per day, and we only have 57. We don't have to individually interact with that many of them before it looks like we're everywhere.
Everyone who is a moderator on the Stack Exchange network is completely voluntary and there is no pay. You may see employees with moderation privileges, but being an employee is not the same as being a community moderator.
For question two, Stack Exchange is also built on a system of community moderation using a reputation system the more reps you earn the more privileges you can gain. This means that the users who are doing those task you mentioned don't have to be moderators. The regular users can also do moderation task as well. Therefore taking some of the load off the moderation team.
Although it says Stack Overflow it still does apply to the SE network as a whole.
Stack Overflow is run by you! If you want to help us run Stack Overflow, you’ll need reputation first. Reputation is a (very) rough measurement of how much the Stack Overflow community trusts you. Reputation is never given, it is earned by convincing other Stack Overflow users that you know what you’re talking about.
This is taken from the blog post titled A Theory of Moderation.
A second case for question two is that a site may not have as much activity which can allow the moderators to watch over the site and keep things under control more easier.
