I bought Rhino which is a 3d solid modeling system for under $1,000. It works well and you can export DXF files to any other system you may have. The CNC mill will probably come with some type of "canned" CAM program installed. Use this to learn the basics before you invest in higher priced CAM software packages. It will take some time to get used to whatever you buy, so learn to use it before you move up to something better. Remember that it all starts with a good model and nothing you do later can correct a poor beginning.