I started out as a mustering pilot and yes I was a stockman in a previous life (before aviation) so I got "in" very quickly compared to some other guys I have known. Most of the operators prefer to employ experienced mustering pilots (of course) but when the supply is short they will take on a guy with the right background and attitude. The attitude is thats its easier to make a cowboy a pilot than it is to make a pilot a cowboy. I dont mean cowboy in the rogue pilot sence of the word, but in the cattleman context.
However, I know of several guys who were not of the typical mould but still given a start with mustering companies in OZ. In those cases it was a matter of right time, right place and right attitude. Dont let anyone tell you it cant be done, if it was easy everyone would be doing it right? So if you want it, find out what you need to do and go get it!
Good luck, enjoy the ride. Its a good one.