congratulations on your certification.
Aside from all the excellent points of my colleagues, I suggest that you also look at the business side of personal training. You do not have a profile here, so I cannot see where you are on that. If you are not working for a gym, the things that some to mind is setting up a business and getting liability insurance. Most certifications include some business advice and will have some suggested forms that you can use as a start.
Your question has been posted on this forum a few times before. I would browse those as well as they contain great advice.