Chris, I'll try to answer your questions, but first I'd like to welcome you and your wife to Canada! BTW, I love Belfast; the people are friendly and there's always lots of Guinness! Hopefully, you'll like it in Orillia (I grew up in Aurora and Richmond Hill).
You certainly picked the right school! I helped Bob Landry put together this program and taught there part-time while I was the Diving Officer (Navy) at DCIEM in Downsview. Since then, the school has developed an excellent reputation in the Commercial Diving Industry. So if you want to be a Commercial Diver, it's a great place to start. The program is designed to give you real usable skill sets, as opposed to putting in time so the school can just make money.
Regardless of where you go for training, you still have to land a job. 'The ticket' isn't any guarantee of getting a job (anymore than university graduation from Harvard or Cambridge ensures employment). You have the basics, so what do you have to offer? Obviously a good school (like Seneca) answers many but not all questions of the employer...
I've hired quite a few Divers in my time. What always seemed to amaze me were the many applications coming from people with a ticket, but with no construction related experience. They took a course and did well, but never worked on a construction site! They never worked and got their hands dirty! I don't know your history, but a background as a Welder or Rigger would go a long way toward employment.
Once you graduate, you will be licensed by the Diver's Certification Board of Canada (DCBC). This certification is recognized by Australia (ADAS), France, Norway, South Africa, the United Kingdom (HSE) and the International Marine Contractors Association (IMCA). It means you can go anywhere in the world and work within the limits of your certification. Where you work largely depends upon wither you want to work on or offshore. Income is dependent upon the area and if you are working under contract, or as an employee of the company.
In any event, you will have to Tender for a period of time. This requirement applies to everyone and time can range from a couple of months to a couple of years. So how much do you make? Well it really depends... Statistics Canada will tell you that over 60% of Commercial Divers make 'over $50,000 a year' (their highest category of classification). But there is a huge variance. Many Divers do it because they like the life-style. Most Divers end-up working under contract and it's feast or famine.
When I went to the oil industry, I was surprised at how little I ended-up making. I did however perceiver and got licensed as a Diving Supervisor and moved into saturation. Money improves at each step. I was among the fortunate to be offered a permanent full time position with Global Industries, one of the world's largest Diving Contractors (now Technip) and for me opportunities continued. When I left them I was the Diving Director, India and Pacific Region with an annual salary of $350K plus benefits like an office (Jakarta), home/household staff, limo/with driver and access to the corporate jet (a long way from doing a two mile ocean training swim with the Navy). When I left, I made more as a Diving Project Consultant to Big Oil.
Where it all goes is like many jobs. It depends on you, luck and the direction the industry takes in the future. Personally, I think that the industry will continue to grow (although at times in fits and starts). I'd like to wish you luck in your quest!
Wayne