PSAI? Never heard of it!
When you say "legit" I assume you mean a recognized agency in which your C-card will be accepted world-wide? From an international standpoint, PSAI received an ISO 9001 rating. The ISO 9001 rating is an internationally recognized standard for quality management in which the organization has demonstrated that quality assurance for its customers is of paramount importance. Also, to my knowledge, every PSAI program received ISO approval which is not true of every agency. I may be wrong, but I believe that every program we have was given an ISO rating. I can double-check for you if you'd like? But, for sure PSAI certifications should be accepted globally without hassle.
When I show people my PSAI C-card, I get instant props! But, that may be because my number is 007?
To answer your questions about becoming a PSAI professional ...
Like most agencies, a PSAI Divemaster candidate may enroll in the DM course after having CPR, First Aid, O2, AED training, 50 dives, nitrox and rescue training. But, PSAI DM's may only be trained by "Master Instructors" which is PSAI nomenclature for instructors who have been specifically taught to teach the PSAI Divemaster program by a PSAI Nitrox Instructor Trainer or above. Unlike some agencies that allow instructors to teach the DM program after proving they can teach an OW course, PSAI instructors must go through training and evaluation for some levels while others may be upgraded on paper with enough training and experience. Teaching the DM class requires an instructor to receive added training from an instructor trainer.
A PSAI Master Instructor will have been taught how to teach a quality open water program, advanced open water program and 5 specialty programs prior to learning to teach the DM program and being awarded the Master Instructor rating.
During, or right after your DM training, I highly recommend taking the PSAI Technical Emergency Analysis & Management course from an experienced technical instructor due to the fact that DM's encounter more and more technical divers while on the job. Knowing the proper way to rescue mixed gas and rebreather divers could save a life.
To become an open water instructor, a diver needs to have at least 100 dives in no less than 6 months, be a DM and have assisted in one complete open water course, and have current rescue, CPR, First Aid, AED and O2 training. The course is a minimum of 7 days and only allows you to teach the open water class.
In order to teach advanced open water and specialties, you need to be trained in each at the diver level and if you are a newer instructor you are most certainly going to have to pass an instructor qualification course in each specialty taught by an instructor trainer. Only highly experienced instructors (usually from a technical background) may apply for sport level upgrades without attending an IQC.
Some specialties require attendance at an IQC no matter how experienced and trained you are, while other, less critical, specialties may be given headquarters approval on paper. I think it's a healthy balance of quality control for the diving public if the instructor receives special training in critical specialties while not busting an instructor's 'nads for EVERY specialty. The skill level for one may be exactly the same for another with no reason to run an IQC as long as the instructor can prove proper training and experience. For example, an instructor who is an experienced cavern, night, and wreck diver could apply for a paper upgrade to limited visibility instructor and probably receive that rating. But, would most likely be required to attend a RAPID rescue instructor IQC.
Even though I'm a training director, there are still courses I need to take an IQC or ITC (instructor trainer course) to teach. Currently, that would be higher level narcosis management programs.
Since PSAI is a smaller agency, it's nice because you are a person and not a number. The agency backs almost every effort you'd make to promote quality education and find ways of making sure you received the mentoring you need to grow as an instructor from those who really know their stuff.
