How do budding system administrators learn their craft? Especially if:
it's a hobby, not something learned in school
they're unemployed and don't have access to server resources?
understanding of the theory of networking. Lots of books and online materials on the subject.
practice with networking
Ways in which they would learn:
they own hardware
in 2010 almost everything is virtualized, and relatively cheap
if you have access to the Internet, you have access to stuff like Amazon EC2 which can quickly provision and spin up/down instances