Minimum PC configuration

I plan on building a CNC plasma machine. I am concerned with minimum configuration machines and hardware. I have a number of keyboards and mice that are wired and wireless. Can the RF be a problem with wireless? Are solidstate drive better than HDD for the same reason? I purchased PC's at auction that were replaced buy a school system. I have complete PC,keyboards, Monitors ect. The harddrives were removed. All of the computers have parallel ports and external SATA interface plugs. Advice is welcome.

Mac