DON'T QUIT YOUR DAY JOB!!! The scuba diploma mills (in my opinion, and I hire scuba professionals) do not adequately prepare you for a job in the scuba industry, they only prepare you to hand over lots of bucks. Also, tell us more about yourself. What is your certification level? How long have you been a diver? How old are you? Are you independantly wealthy? Do you have bills/other mouths to feed? Do you mind living in cramped quarters for months to barely make gas and beer money? The diving industry can be very rewarding, but most of the rewards are non-monetary. You can't eat pretty dives, you gotta have a little cash coming your way, too.
Teaching scuba is teaching a life-support class. If you're not properly prepared for all of the issues that could come up, you could end up as a lousy instructor that are reviled on this very board. Get lots and lots of dives under your belt, in a quarry, in cold water, in low vis, in the ocean, in the current, etc. before you take the responsibility for someone else's life in your hands.
At the end of the day, I would look at an instructor that came out of one of the diploma mill institutes as having a liability to overcome rather than being properly prepared to enter the industry. There are, of course, exceptions to this rule. The better prepared you are to enter one of these programs, the more value you will get out of it. I see a few posts on the Scubaboard about "Why can't I get a job, I just graduated from XYZ Scuba Academy". A lot of scuba employers look at diploma mills the same way I do.