BTB contacted me with this question that you have. I haven't been as active as i used to before on the forums but BTB thought I could give some insight on this topic.
Do I want to do it? Why? Why not?
You become a strength coach because you love everything there is about strength and conditioning. From strength training, speed, plyometrics, to nutrition and recovery/rehabilitation. Unless you get a job at a division 1 school, pro level, or have a successful business such as joe defranco, we as strength coaches don't go into it for the money. Our hours start before the sunrises and we are done when everyone heads to dinner. You practically live in the gym and barely spend time at home. I'm not trying to deter you away from thinking of going in to the job. But you have to really want to be a strength coach. I LOVE IT!
How do I go about it?
All of great things have already been mentioned. You can get the degrees of course, certifications is a must, but overall experience is essential. You can't just be someone who works out, you have to be more than that. You have to be a leader. Since you were in the army, you know all about what it means to be a leader. That is what a strength coach MUST be.
It is important to read up, but also start talking to other strength coaches. If you have a college or high school in your area that has a strength coach, contact them and see if you can meet up and ask them questions. Look at is as an informational interview where you learn more about them and their path in to becoming a strength coach. You never know, it may land you a volunteer job there which is a great first step.
What type of careers could I expect?
Depends on what you are interested in. Ive done group instructing, personal training, and strength and conditioning job. I prefer to work with athletes. Presently, I'm the head strength and conditioning coach at a small private college in southern california.
Hope i gave some helpful points. Best thing to do is try to volunteer at a local high school or college and see if this is actually something you want to pursue. Best of luck!