Personally I wouldn't go for the eBay link.

To me it looks like a DIY effort made from box section extruded aluminium and will wobble more than Jessica rabbit. My guess is that the project started off as a little project with a dremil or similar engraving tool and having realised that would them nowhere they have tried to improve the machine by getting the most powerful spindle they could find only to find that the machine shook itself to bits so they have given up and decided to sell it all.

You will notice that the support rails (those two outer bars running down the middle) look thin and have no support. This means when the machine moves to the centre the the rails will flex causing the Z axis to change depending on the positioning.

If you look at the pictures in post #32 you will see that machine has rails that are supported, i.e they are mounted on the solid base with an upright section supporting round bar. This is the next best thing to having square rails as it reduces the deflection of the bar as the mechanism moves to the centre.

The way I see it you have three options, buy a very cheap machine and use it to experiment with machining forget about metal and use only soft materials like plastic and wood and put up with some of the problems and limitations that you will get along the way. Then if you find it is something you want to get more involved in put the machine on eBay and buy something better when you are ready.

If you are serious about making a go of it but have not got the budget to go for a real high end machine then try and get a half decent machine that is built on a sturdy cast base. This should be enough for a reasonable amount of hobby work to an acceptable standard.

Go in at the top and buy an all iron heavy duty milling machine that will do everything including steel and take out a mortgage for it.