Clouddancers --
Well, to be an SSI instructor, you would have to log at least 100 dives before you could begin teaching in addition to the training itself. So, excluding the cost of all of those dives, figure $250 to get your original certification. Then you'll need four advanced specialties at $85 each plus diver stress and rescue for around $175 to get Master Diver (requires fifty logged dives in addition to the specialties and rescue), then you would need to get your Dive Control Specialist certification which costs around $450, plus you'll need to get CPR & First Aid as well as O2 provider certification (figure another $100 or so) and finally your instructor training for another $1250.
All of that is excluding the costs of diving and the requirement for "professional quality" equipment you HAVE to own. Now, once you have all your training and at least 100 dives logged, you'll need to get an instructor certifier to sign you off and that will be another $500. In addition, there are annual fees you pay to keep your certification current and you'll have to carry professional dive insurance.
Help me out everyone... did I miss anything?