I have been self employed for most of my life as a Unix/Linux consultant doing SCO Unix and Linux, Solaris, Mac OS X and a few other things.
I don't call myself a "wizard" or a "guru". There are such people, but the real ones are few and far between. I would hesitate to use the word "expert", too. Certainly I have some expertise in some areas, but I know there is always someone else who knows more about any given area than I ever will.
I'm now what I call "PMR" - Pretty Much Retired but still enjoy writing about self employment and computer technology.