Two things,
Divemaster UK,
The only person that can guarantee you a 100% pass rate is YOU, and any Course Director who claims a 100% pass rate is probably exagerating.
I have been teaching PADI Instructor courses for six years now and there are always people who arrive at IDC´s and IE´s unprepared or with the wrong attitude. There are always the odd one that need to take a little longer to study, or repeat certain parts of the exam. That is ok, we value what we work hard for and dont value things that are easy or free.
In my case I guarantee to make you an instructor, no matter how long it takes and the second IDC is free. If you need a third or fourth one, I may consider that it is not entirely my fault and that you need to pay a little extra for my and my staffs time. That is just me though, this is also common on open water courses. the course normally costs (for example $300) and it normally takes three or four days. If it takes longer or more work than normal, then the instructor may charge some more for the extra time.
I have had people that became instructors after struggling with the theory and language, I find this particularly when teaching the local market in developing markets, some of my clients have little or no High School education, this means that they sometimes take longer to reach the level that somone with more education might find easy. Similarly with Europeans and North Americans, they tend to have plenty of education, but dont have the 1000 or so dives that the local divemasters have, so they need more development in the water.
If you want to become an instructor, you need to understand that if the student fails to reach the required leve, we should look to see if the instructor failed to teach what was required. No one should fail a PADI course, whether DSD or IDC. The only person I cannot teach how to dive or be a dive instructor, is someone that does not want to be one.
Point Number 2
Ian, Dude, you are depressing me, most people who want to make lots of money become civil lawyers or stock brokers, but that doesnt mean you cant make a good living while having a diving job. If you cant make any money, you need to diversify your skills. The company I work for has instructors that make between $4000 and $10,000 USD per month. that is top end, but the average is $2000-$4000 USD per month.
The truth is that working in the dive industry, you need not only to work hard, but you also need to work smart.