I would recommend talking to some local teams in your area that have been around for a while. The current control system will become obsolete from a FRC perspective and you may be able to convince them to offload an old power distribution board and some illegal, but functional, motor controllers (Victor 883) or even some of the old 884s.
As for motors, are you looking for CIMs, those may be hard to find at a goo deal. But there are plenty of DC motors you can but on the web - it all depends on what you need.
As for batteries, buy a new one. They aren't that overly expensive, you should be able to find them around $30-35 (
example).