How to get started
You want to start with getting certified with a reputable certifying fitness company. I wrote a post on the most affordable group instructor certifications. If you have a science background or you have been consuming fitness information for a while, it won't take you long to read the study book to pass the exam. If you have no physiology or anatomy knowledge, it might take you a little longer to get familiar with fitness information. It can take you from a month to year, depending upon how much time you devote to your studies, to prepare for the exam.
You will also need to be CPR and AED certified in order to take the test. You can start with that test first because it doesn't require a lot of study.
After you are certified, I would advise you to put together a fitness class, something you are interested in teaching and plan practice classes with friends and family members.
Working for a fitness club
When you feel like you can teach and ready for the public, you can apply to a fitness club chain or a local community recreational center. The pay can range from $15-$60 an hour according to where you live in the United States. Your salary will also depend upon the fitness club too. High-end clubs will pay more but you will have to have a lot of experience or a lot of charisma and confidence.
Most instructors have a full-time job and they usually teach before or after work. If you are self employed and have a flexible work schedule, consider teaching at non peak hours. Some clubs have classes at 9am, 10am, 11am 12pm and/or 4pm and many times fitness clubs have a hard time finding instructors to teach at non peak hours.
Setting up your own fitness business
This is where you can make some good money but you need to have a venue and a following. If you have this, consider instructing your own classes. For example, I use a community center to hold classes. It costs me $15-$25 (size of the room) an hour to rent the room. I charge $55 for eight monthly classes.
Rent: $25 x 8 sessions = $200
Income: $55 x 15 participants = $825
Net income before taxes = $625 or $78 an hour
As you can see, you can make more money being on your own but you have to constantly market because people will drop out. You may have an upfront cost, especially if you supply any equipment like bands and weights. An option to this would be to have the members buy the equipment from you so you can keep your costs low.
As you can see, being a group fitness instructor can be a lucrative and a healthy side hustle. Get started today and have fun along the way.