Ocean Divers in Key Largo will take 26 days; AOW(2 days), EFR(1 day), Rescue(3 DAYS), DM(7 days), Dive Theory Prep(1 day), IDC(10 days), IE(2 days). There are no days off, even for the session starting Dec. 26.
You have to be 18 years old with 20 logged dives to start the DM course; 60 dives to be certified DM. At a Career Development Center (CDC), an Instructor Candidate must have been a certified diver for 6 months and can start the IDC with 60 dives; 100 logged dives required to take Instructor Exam (IE).
Another 6 days gets you; EFR Instructor(1 day), DAN Diving Emergency Management Provider Instructor(1 day) and 5 Specialty Instructor ratings (MSDT Prep - 4 days). Still no days off.
They will continue to take your money for further training, all the way up to the IDC Staff Instructor Course; that does require spending some time as a working Instructor, you can't just take a course for this one. They have been doing it a long time; If you apply yourself, a sharp, athletic, water person who is good at teaching will have a very good foundation to go out and start learning how to teach diving, by teaching diving.
In that area there are plenty of significant brains to pick for the history, science and teaching of diving, and much, much more. Try to hang with them and you just might learn more about diving than the 1000 dive "local diving" DM who shows up just to do the IDC/IE.
I stayed 6 or 7 weeks and logged over 200 dives. The conversation over beer at Sharkey's was probably the best part, but the diving was pretty educational and challenging too. The high cost does a good job of weeding out students who are not motivated and capable; the few true noob's that do sign up do not make it in one session, or even two.