Jobs in Colorado casinos are great. The pay is usually high (much higher than the city) because of the nature of the industry and also there is a large travel expense to work in Black Hawk, Central City or Cripple Creek unless you happen to live in these mountain communities (which makes it even more profitable!).
You must be 21 to work in the casinos for positions related to any gaming activity. Exceptions are made for F&B and non-gaming positions such as house keeping and the parking lots (valets, etc). In addition to being 21 you will need a valid Colorado Gaming License which you can apply for here.