You can buy an already trained dog, but it will cost a fair bit of $ and then train a pup off it. It depends if your after a bailer or a Lugger. Be warned, the dogs in the adds may not be what they are made out to be, ask to see the dog work first (finding on its own if possible) and get a money back agreement if possible on paper, otherwise wait until another comes along. The dog needs to be stock and wombat and roo proof.
There is not much more info I can tell you I don't think to really get you started.