Starting out at 24 Hour Fitness
24 Hour Fitness is a good place to get your start. The training is decent if you have a good Manager. They also use NASM as their personal training template. I have a very good Manager.
The down side is you must be a good sales person who can close a deal. Most members express sticker shock when they discover the cost of a 10 or 26 week program. If you can't be convincing, you won't do well.
24 Hour also pushes other sales such as vitamins and other products. You must have the ability to be a good trainer and a good sales person. Word spreads fast if you are known as a good trainer or a poor one. So make sure your first few clients will be successful for you.