Some unsolicited but practical advice if you are thinking of designing and building your own CNC;
You wont know all the answers before you start, you wont even know all the questions. Start anyway it'll be the most satisfying thing you ever build.
Just say no. Stay at home and set fire to £20 notes. It'll be a lot cheaper, less stressful and more enjoyable.
Your experience will be somewhere between those two axioms and probably encompass both.