Some very interesting replies!
I guess I'll have to spend a few weeks thinking about things.
A lot of you have implied what I thought at first, that it is becoming more and more difficult to find something that can be CNC made at home and still produce a profit when the competition is so well equipped in comparison. QVC for instance - Sparkly things for $9.99. Doesn't matter if it's junk, since the camera doesn't pick up on it. Once you've bought it and found out it's junk, they have your $9.99 anyway.
Ironically, TV shows like QVC are making out more and more that the home office is the place to make money with services like eBay available to it. Probably because they sell the printers and paper to put in your home office. As well as the burgers for your dinner after a hard day in the office!
There are also the physical problems of competing with big companies. While I'm sure even I could afford to build a gigantic plasma cutting table with the help of a loan, I don't have a room 60ft long to put it in. The only way of competing with that is to have a 6ft long machine that runs ten times quicker than their's. A linear motor fed plasma cutter!
I am moderately hopeful about my idea with plasma cutting. I have actually been talking to my brother, an IP lawyer, about possibly getting it patented. The idea is based on increasing the definition of the plasma. However, there are at least a few mechanical problems that would need thinking about before the idea could be applied properly. I know for a fact that no company currently sells plasma torches in this layout. While I am thinking about ideas, I'll buy a plasma cutting and give the theory a test.
One thing I have been thinking about recently is where all the millionaires are.
There are a few making super expensive products, like Bugatti Veyron super cars, things that sell in small numbers but cost a lot each. But the majority of them sell wholesale products that everyone needs or wants in mass.
Richard Branson for instance, train tickets, Cola & music. Bill Gates, something to make your computer work - from time to time.
There aren't a lot of millionaires who do custom machining of bits and pieces. Boeing, on the other hand, who mass produce aeroplane parts, made fifty billion dollars worth of profit last year alone.
Perhaps the only way to make a good amount back from CNC is to work towards mass production of low profit per unit parts that have mass appeal?