You only get paid for the hours you are working at the mine - that's correct, however there is also plenty of overtime, so plenty of opportuity to earn good wages. Having said that, mining life is not for everybody. I have spent some time up at the mines working with my clients and the fist time I went up I thought it was the worst place on earth. I have gotten used to it now, but I'm only there a day or 2 at the most. The conditions are really hard, they work regardless of temperatures and weather. The only time they stop is when the rigs are under water. Often there is no phone or internet access, so contact with home can be difficult. Shifts are usually 12 hours on 12 hours off on a rotation basis. Some new starters only make a couple of weeks at most before realising it really isn't a way of earning a quick buck.
If you are looking at it as a quick way to make a buck, I would say, not the right environment for you. If you are looking at a long term career, then it might be the right choice. but you really have to take into consideration all the pros and cons before making a decision.