I’m not sure what your current skill set is, but, assuming you have group instructor skills to run group training, you could go a couple of different directions.
1. You could start by determining what you want to lead and find people interested in that as well.
2. You could start a group based on popular wants and needs that you hear during your current work (but still defer to #1).
I love to train groups and you would be offering a valuable service that’s a win for you and your clients. You’ll be able to offer them the same duration of training while charging less (but you’ll actually make more). They will enjoy the group dynamics and will likely push themselves harder. Many people will also see this as a great chance to train with their families and friends.
As a side note, you could also specialize in specific groups of people like families, bridal parties, sports teams, teachers at a school, etc.
Try to find clients with similar goals; they do not have to be at the same fitness level (that’s where your expertise comes in), but it helps if they are working towards the same thing (run a 5K, lose weight or just feel better). Do everything you can to increase group camaraderie; encourage introductions, do some partner drills, allow time before and after for people to talk. Discuss payment policy upfront (if you have 4 people and 1 does not show up do all 4 still pay or the 3 split the fee?). Keep the personal in; allow modifications for each individual. Enjoy; it is my favorite type of training!