i think you can hire them from boc gas supplies. theres one in o'conner on the same street as kens old shop.
but if you gonna get serious might aswell buy one but they arent cheap. plus i think to get the gas for them you need to apply for a license for it? i know we had too but because we had a workshop they just gave it to us.
btw they arent cheap... you have to buy the mig, then the gas, as well as the wiring, and then you will prob need stainless wire aswell as mild steel wire plus safety equipment etc... it all ads up quick
oh and most of the smaller ones run off of 15a wall sockets too