I have a 3' x 4' home built CNC that I've been running for almost 10 years, and just in the last 2 months rebuilt it with all new electronics and control system.
I helped a friend of a friend get his 4' x 8' Bob's CNC running and set up...just my opinion, if I was jumping into CNC I wouldn't consider any machine made of wood...there is too much flexing going on caused by temperature and humidity changes, to allow for any kind of repeatable accuracy...plus, these machines are assembled with bolts and captive nuts...over time (and not much) as the wood dries out, all the bolts will loosen and cause problems.