Most commercial mill's will need a faster spindle. PCB spindles really need to run high rpms because of the tiny radius of the cutter. The economics of milling pcb's isn't real good. Places like batchpcb.com and olimex.com are pretty inexpensive. Getting fine trace width from milling isn't a trivial task either, especially with the free software available.
BUT, if your looking to learn rather than trying to make low cost prototype pcb's, then I would advise you to look at building your own. Depending on your access to tools, you can use the money to buy components and/or have parts made for you.
Phil, Still too many interests, too many projects, and not enough time!!!!!!!!
Vist my websites - http://pminmo.com & http://millpcbs.com