Hi,
Great to have you interested in a professional career
in diving. A couple of suggestions.
1. Make sure you really like diving. It should be something you enjoy. Its not about the accumulation of credentials. While PADI requires 60 dives for the DM and 100 for the OWSI, my experience tells me that you should have at least twice or maybe three times these numbers before you practice professionally.
2. Make sure you accumulate this experience in a variety of environments
cold water/ warm, boat and shore, salt and fresh under different conditions.
3. The demand for DMs is somewhat less than for Instructors who are willing to DM as well. So my guess is that an actual paying job at the DM level will be hard to come by unless you have considerable experience that is of interest to a lds or boat operator.
4. Diving is part of the tourism and hospitality industry
even the teaching end ultimately. So people skills and a genuine interest in seeing others have fun, become more skilled and generally stay with the sport is important in maintaining a strong student or client base.
5. Finally the money is really lousy the hours are odd and long, and the work is hard
its more about gear rinsing and tank hauling than in the water hours on an hour-by-hour basis. (Only a slight exaggeration)
so you really need to enjoy what you do and find pleasure in becoming a better diver and teacher
that is the process rather than the money or the credentials are what will make you an effective DM or Instructor.
Good Luck