There is the z/PDT, which is an emulator that runs on your PC. It comes with a software pack that includes z/OS, z/VM, and few other things. It runs $900 a year, not sure if there is an initial cost.
http://dtsc.dfw.ibm.com/adcd/adcd.shtml
However 900 a year is still out of reach for most individuals. They should make it free.