No matter what age you are, find a mentor(s).
First you need to decide what areas that you want to specialize in and then you can start setting your goals in this field.
When I was a group exercise director at a YMCA, a had a woman who was in her 60s and who was retired a Human Resource Rep. taking my Ballroom and Cardio Dance classes. As our friendship grew, I thought she would be a great instructor to take over some older adult classes. After several discussions, she was interest. So I took her under my wing and trained for about 4 month. She was a sponge. Other staff members did not see the potential that I saw from day one. After the intensive training, everybody wanted her in their department. She built her way up to full time and I was still a part time employee. i no longer work for that job but she still does. She now has about 5 certifications and had been working for about 3 years at the YMCA.
A man in his 70s decided to become a personal trainer. He has earned in AFAA certification in personal training.
You will be a blessing to your clients.