I have been looking into this myself for the past few months or so. Basically the cost of the machine will determine how much capital you need. To get started, you will at least need a machine, a compressor, tooling, computer, CAD software and some kind of workbench/storage cupboard. I reckon it is the cost of the machine plus about 20k. Used & New Heavy Industrial Machines, Machinery & Equipment for sale at Australia's No.1 Online Machinery Market has good second hand stuff. Plus you also need somewhere to put it, get it installed, etc. Theres heaps more involved than you think.