I think becoming a personal trainer could def be a career option for you. I now do personal training part time as well. It is a very rewarding career. Your clients will come to you with all sorts of goals. To lose weight, to get stronger, wedding boot camp, the list is endless. You are not expected to train the sameway as you train your clients or have the same goals as they do. However, to be successful you will have to look the part. If you are 50 pounds overweight eating fastfood infront of clients, you will not do well. If you are preaching a healthy lifestyle, you need to be living one yourself.
A good certification will teach you how to train a person that doesnt have any disabilties, diseases, serious injuries or health problems. It will teach you about personal training, program design, and sports nutrition. After you become certified, you take additional certifications to further your education and can specialize in different groups of people such as children, teens, young adults or senior fitness, or other topics like sports medicine, or group fitness.
Look for a legit, respected certification. There are certifications that cost $50 dollars and don't require an exam..tempting but avoid. Go to a gym in your area or the place you plan on working and see what certs they accept so you dont waste your time and money. I highly recommend checking out the IFPA. Their certification is practical, real world based. They give you a ton of info on creating workout plans for each of your different clients goals. One size does not fit all in the fitness industry, you'll need specific workouts for each of your clients!