A Taig, or Sherline. might work but the x/y travel is smaller than youre looking for.
the taig is 9-12" X 5.5" depending on the model.
Ive got a taig myself and like it quite a bit.
also remember that milling aluminum has a bit of a learning curve to get feeds & speeds dialed in
you'll probably also need a butt load of extra equipment:
work holding (milling vices and clamps to hold the vice or stock to the table)
tooling (end mills, drill bits , fly cutters)
dial indicators (to line up stock)
edge finders (to zero the bit on the stock)
dust collection especially if working with wood
a dedicated computer
and of course the stock itself.
some precision machines that use lead screws (which is most of them in the 5000 or less price range) will also need to have their backlash nuts adjusted occasionally for wear.
wood is a bit easier to work with, i just clamp down a block of pine and run my code.
you might also want to look into CNC routers