I don't know if you can get used equipment. As far as new low-end Chinese lathes and mills, you might look over the items and prices here:
http://www.grizzly.com/products/cate...spx?key=460000
http://www.grizzly.com/products/cate...spx?key=480000
DROs and mill tooling aren't cheap.
Either one can be dangerous. Here's something I came across about a year ago:
"There was a "very serious" accident at the local high school last week. I use the quotes because I have not heard clear details yet. In fact, my account may not be accurate, but I don't think it matters for the purpose of this discussion. One member of the school robotics team (15 total) was running the lathe, and while bending over to look at her work, her hair tie snapped and her hair got caught, pulling her right in.
Update: The girl was released from Stanford Saturday afternoon and is now being considered for a unique operation to try to save the ends of 3 fingers which were caught in the windings of her hair as it was wrapping around the auto feed screw."
The cost for a setup to weld Aluminum will vary with the process (MIG or TIG) and what thicknesses you need to weld. A 175 - 200 Amp MIG welder would be the minimum I'd recommend for around 1/8". A spool gun is an option to consider, as a regular MIG gun doesn't feed the soft wire very well. Here, a minimal MIG setup is perhaps $1,000-$1,200 with a tank of Argon. The least expensive unit with a spoolgun:
http://www.northerntool.com/shop/too...2663_200392663
TIG is considerably more expensive. About the least expensive unit I'd consider is this one:
http://www.millerwelds.com/products/tig/diversion_165/ Add gas, Tungstens, filler and safety gear and you're talking $2,000. Safety issues include fire/arc protection and handling/storing high pressure Argon.