I have been diving for 24 years, have thousands of dives, have dealt with students in the military, public safety, and recreational area, and STILL find it hard to find a good job in the field that is steady and regular. So to increase my marketability, I am doing my MSDT. You will find that in this industry, you will get back what you put into it.
Just remember, that the most important thing to put into any decision is your desire to be a part of something. If you love the sport, which it seems you do, then persue it. BUT... If you are looking for a solid paycheck, benefits, and the glory of being an instructor, then you are in it for the wrong reasons. As one poster said earlier, most of us merely work as DMs on board the boat, yet still have to carry instructor Liability, which can be three times that of a DM. Then there is the cost of the IDC you have to consider, the materials, the IE, and the cost of maintaining equipement for students if you dont work in a shop.
If you spend $2500 on an IDC, and then your roughly $550 on insurance, and do 5 students a month, you are chasing to make up that money you just spent.
So take some time and decide if you want to teach because you just love to teach, or if you do it just becasue you like being in the water. I can tell you one thing for sure... when you are in the water with students, it is not a pleasure dive. It is work, and usually only on the last dive when the student has the dive to themselves after the proficiency dives are you able to relax and enjoy.
My suggestion is to get to DM, and stay a DM for a minimum of 250 dives before you task yourself with being an instructor. Why the number of 250? Because that is normally about 2-3 years for a lot of DMs who are working in a non-resort location where you are not diving on a regular basis. Plus, it will give you a chance to figure out what course and path you want to take with your diving future. Do you want to teach students OW, or do you want to teach mainly specialties and advanced courses? And being a DM and holding liability insurance will allow you to be in the water with your OWSI or MSDT and "assist" them in certain areas underwater. This will give you a chance to see exactly what challenges you might face with students underwater.
We are more than happy to help you down your path in the diving community. All you have to do is ask, which you did. And that is more than a lot of people would have done. For that, we commend you, and open our world up to you for whatever help you might need
Phil