If cars and mechanical things are your hobby then I have to say "don't make your hobby a job", it'll quite likely destroy your enjoyment of the hobby.
Years ago I wanted to get into mechanics and so on and was very glad the place I did work placement/experience at told me this.
As for the mines And FIFO...
Been there, done that. If you're young have no commitments and don't get into the trap of spending what you earn you'll do well. Set yourself up then be prepared to go back to a normal wage.
But the wage comes down to you working long hours, being away and having nothing else to do.
The roster as mentioned earlier in the thread plays a big part too. Even time is what alot of people want and they still earn well and are home for a good length of time.
Did I also say, be prepared to be filthy in dust, oils, grease and the mix of all 3 if you do go that way....
If you are hellbent on getting into a mechanics job then go for it. If you're looking purely at the dollars then it might not be for you.
One of the younger guys I've known through sports is a diesel mech apprentice (Buses) and enjoys it. Is happy with it and is learning lots with a decent wage. All comes down to where you get in and how you approach it.
Aim high with whatever you do.
Don't make your hobby a job.
And if you do, don't get suckered in to the snap on truck....