Apologies for the late reply.
I was a Linux support guy at 18, moved into sysadmin roles for a couple years, then quit my job to go to college. I was supported by my parents so I did not work my way through college the way you likely envision.
I did, however, work part-time as a sysadmin all 4 years (20 hours a week), but it only funded some living expenses, not my education.
Also not what you're looking for, but, while I was still young at 21, I thought I'd have a huge leg up on all of them 18 year old youngins. Turns out we all liked pretty much the same music and the cool kids were still cooler than me, and the guys good with the ladies were still better at it than me!
I majored in information systems and am still doing the same work today, 10 years later, but I love it and wouldn't change a thing. I wasn't ready for college at 18, and I got a lot more out of it and was more sure of myself at 21 when I enrolled.
I rarely think of college as improving my career, but of course my degree from a relatively prestigious 2nd-tier private school doesn't hurt my resume.
I pursued a professional services track upon graduation and it took me about 1 week to say "fuck this", and 2 months to quit and go back to sysadmin/ops work. If I had no previous work background I wouldn't have known that my new role wasn't right for me -- at least, not so quickly.