I’ve noticed from reading magazines that artists usually use other applications to complete their work. Is it necessary to go back and forth from zbrush to something like Maya? Can a model be made from beginning to end just using zbrush. I ask because the only other program I have is a student version Maya 2008.
You don’t need to have another 3D package, but it helps. Especially when you are used to conventional Poly Modeling. Of course you can create an entire character completely in ZB. You just have to plan your Polyflow really well before hand. (well actually you always have to do that 
)
When it comes to modeling, Blender might help you, as it is free.
Now rendering is another story. Most people would use an external renderer. Be it Max, Maya, Modo or Lightwave in my case. Another nice option is the Maxwell renderer, it’s just kind of pricey. I am not saying the ZB render engine isn’t any good, in the contrary, but especially for stuf like SSS (subsurface scattering) or exact lighting, i would prefere an external renderer.
Read your post about schools btw. nice to read such open words. I am self taught myself, which cost me a lot of time and money (and still does) but it is also very rewarding as you don’t rely on other people all the time.
Hope that helps and good luck to you.