Homebrew PCBs

I have a question that I am sure will create some sort of 
controversy... so I apologize in advance. However, I am considering 
making a CNC device (probably using a kit), for low usage level use 
in particular for making PCB's.

My question is this:
- Which is the best CNC software to use on a hobbyist production 
level (low), for making PCB's, on a very strict budget (lower $$$ = 
better)?

I understand that some features may be indespensible and may cost 
money. I am just looking for the best $/benefit ratio (where ZERO [or 
a negative number -- theoretically] is the goal) for CNC software for 
use on making PCB's.

As a side question: Is there a particular kit or completely built 
unit that stands out as being "heads-and-shoulders" above the rest on 
the same $/benefit curve?

Thanks,

Bob H.