You want to know how people started so I'll tell you. In the early 1980s I got a 300 baud modem. I began calling Bulletin Boards Systems. One of them was a board with a private section which I gained access to after chatting with the sysop. It had "codez" that I could make free phone calls with.
I got busy in the mid-1980s, but in 1989 I began calling BBS's again. I started calling boards with h/p sections, or totally h/p boards. One one of them I mentioned the dialup to a local university, and what I saw on the various menus I could get to. Someone responded to my post (this person later became the CTO of a company whose worth was in the billions). He gave me the hostname, and a username and password of a SunOS box at the university. I logged in. It was the first Unix I ever logged into.
Anyhow, fast forward to early 1996. I have hacked the account of someone who runs a local ISP, who I dislike. I am reading through his e-mail and various files. One thing I see is his Usenet spool of the local tech job postings. I start reading it, and see an ad for a company. The company is a new ISP which is about to expand from extremely small to slightly bigger. It sounds so small and poor I think I might have a shot. I log back into my legitimate systems, and send an e-mail to the ad placer and say I'm interested in a job. I say I know Unix well (true) and that I complete my college and have a computer science degree (not true). When I meet him, his wife's friend is there, and I happen to know his wife's friend, so that was luck for me as well. So I get hired. The main box is a Linux pre-1 which got upgraded to Linux 1.X on the first week of work. We also purchase a used Sparcstation IPX at a good price.
And it's gone on from there. The most I ever made as a Unix sysadmin was over $90k a year. Although adjusted for inflation, the highest I got in an adjusted for inflation sense is $110k.
Unix administration was really hot in the ISP and dot-com go-go days. Not so much any more. Of course there's jobs out there. People are trying to do more "in the cloud" nowadays so that lessens work to some extent. There really wasn't as much good turnkey web hosting and managed colo and the like in the mid-1990s as there is now, so a lot more people had to roll their own. Or shared virtual servers. I have been doing different stuff in IT lately, I have never even worked with some of the "newer" stuff like blade servers. Not that blade servers are that new any more.
Also be prepared to be chained to your cell phone 24/7 and getting calls at 3AM if there's an outage, even when you're not on the on-call rotation. And then have office gossips and nosybodies complaining you're not in the office at 10AM after you took that two hour call, which almost no one will know about. Or having to deal with old, out of warranty, broken servers that have trouble backing up and keeping their data, with no good recovery plan, which no one cares about until they go down - then the bosses will all crowd your desk every five minutes frantically asking you for a time estimate of when everything will be back to normal. Of course other IT jobs, like development, have a different kind of pressure. In some ways system administration is more preferable, as you can only keep servers up 24 hours a day - developers usually have a mountain of desired features piled on top of their workload.