Others might be able to come to your gym with the management's approval. When considering hiring any professional, you want to know his or her credentials. In the case of trainers, you want to be assured that they are certified. Anyone can claim to be a trainer, but a certification implies a certain level of expertise and knowledge. They get extra points for having graduated with a degree in exercise science, kinesiology, or the like.
Several factors can affect how much a trainer charges.
Some trainers include such services as computerized body-composition testing. Others might bring their own medicine balls, bands and body bars. The more frills and technology used for your training sessions, the more you can expect to pay. Finally, some trainers just charge more because they are good. They have been successful at developing a large client base and can afford to charge more per hour than someone just starting out.