A gaming manager can make upwards of one hundred and fifteen thousand dollars a year on average. That's nothing to complain about, except for maybe when you're coughing up smoke from your smokers-allowed casino. Luckily this isn't the 70s where the mobs rules the casinos with an iron fist either. You may not see every dime of that one hundred and fifteen thousand dollars a year.
As far as getting into the business, that could be difficult. There are extensive background checks done on the people who work for the casino even at the lowest level. If you're going to be responsible for handling the gaming operations, you need to be trustworthy to the company. If you have a theft on your criminal record, you're not going to be seeing yourself as the gaming manager any time in the future.