A good, free introduction to CAD is inkscape. I've used it quite a bit for designing various bits of guitars. 
 
	https://inkscape.org/en/
 
	CAM is a slightly more involved subject, but you can use software to convert your inkscape files into a suitable format and then add the depth information for CNC milling. Not wanting to detract from BC, but ProjectGuitar.com have a forum dedicated to computer aided manufacture that contains a wealth of information