I agree,
I would be careful with anything on ebay...and also, what happens when you need support, or something does not go right?
The one in the picture as you can see is air-cooled, and about 1 3/4 HP. Obviously, you can get much more powerful ones, but for cutting wood, I figured this is more than I need. In addition, anything higher, then the power requirements also go up, which means more cable for 220V lines etc etc. I kept it simple for the time being.
Water cooled adds a bit more complexity, since now you also have to run those lines, figure out a fixture for them to make sure they do not interfere with the machine movement, and have a pump with water going. Not a big deal, but will add complexity. You might consider air cooled, but again, these things are NOT cheap! This is the reason why I went with a plain 'ol simple Home Depot Router special to start with, and to my surprise, the results are quite good! Router has very low run-out and I have cut pretty much any kind of wood with it, including inlay, carbon fiber, Garolite etc....it is LOUD however
You are going to love the accuracy of a CNC machine!