don't bother.
milling requires a very sturdy machine as you are trying to take off just the copper and not dig into the board.
a high quantity carbide cutter will dull quickly when cutting through the fiberglass of the board.
you will need one new cutter for every 2 or 3 boards and the cost will get pretty high pretty quickly.
the dust of fiberglass is a health risk so you need a HEPA vacuum to extract it.
lots of home vacuums have HEPA filters, so that is good, but they can be expensive and the dust is so fine, it will clog them up too.
also, unless you have a very flat sturdy board, you will have a hard time getting traces thinner than about .02 inches and you will not get traces to pass between pads.
consider the iron on method to etch boards. the quality can be high as you get better.
but, if you were to build (or buy) a simple x/y table with some sort of drilling head you can make perfect holes for through hole work. the driller does great things for DIP chips and such. I do recommend an X/Y drilling machine to compliment your etched boards.
double sided is not that hard as you can have reference marks on your transfers and line them up when you do the heat transfer.
I am on my second T-Tech Quick Circuit and I send out my boards as it is cheaper and easier and you get plated holes and silk screen for little more money than a make-at-home board. the spindle on mine blew apart and I did not want to spend $1,000 for a new spindle from T-Tech. I made up a simple DC motor spindle and it mills and drills acceptably.
The flatness of the hold down and control of the depth of cut cannot be understated for prolonging the life of the cutter. even that $2,000 machine burns them up.
My first machine was in better shape, and I loved the ramp up of speed for milling and drilling. it changed speed to accommodate the cutter and drill sizes.
But, I honestly I like etched boards much better. I don't like leaving 99% of the copper on the board because all the miller does is make an outline.
and I cannot underrate the value of solder resist applied professionally.
On the pro side, I do like being able to make a board and not wait for shipping.