I had the other side of this talk one day on a boat off Cayman with our DM/Instructor. At the time he was working as a DM 5 mornings a week and teaching resort courses in the afternoon. Here's what he related: (some of my comments as well)
First of all Cayman is hideously expensive if you stay near the tourist areas. Almost everything is brought in by ship so food is 2-3 times U.S. prices. And most of the condos cater to the tourist crowds so they're rented by the week. The DM told me that if it wasn't for the free happy hour buffets at the resorts, he probably would have starved the first three months he was there until he got his bearings. However in his case, he got his job offer and moved down there within about 2 weeks, so with better planning it's probably not as big a shock. He did tell me that his mom still ships him dry food occasionally. And he lives in a small, local house - he stressed the word small - about 5-10 mins. inland (nothing in Cayman is very far inland) with 2 other people to save money.
Cayman is really known as the offshore banking capital of the Caribbean so despite it's reputation as a great dive location you can pretty much figure that where there's that kind of money, prices will be higher. Although the local people do seem to survive there, I don't think a lot of them make any money. Plan on being one of them if you get a job there. So it's a question of what are you willing to give up to pursue a diving career. If you read elsewhere on this board, you'll find that most dive professionals have other careers and dive on the side, or have the resources to work for less money.
And post-Ivan a lot of Cayman is still recovering, so I'm guessing a lot of the more affordable accommodations are either still damaged or gone, but it might also be a good time to go there and find affordable housing since the local rental agents might be a little more desperate than normal because people did leave the island either temporarily or permanently when their housing was destroyed. I'm contemplating a trip there this summer and expect it to be far more reasonable than when we were there in 2003. I could be wrong though, it's possible that demand exceeds supply right now.
BTW there's a lot of bartenders on Cayman so don't assume that's automatically a backup source of income. Although anything catering to the tourist crowd is probably a good idea. When the cruise ships dock in the harbor, I think the population of Georgetown doubles during the day. ATM servicing might be a good line of work there, just about every bank has one and there's over 400 banks on Cayman. LOL...
Cayman is a British Crown Colony so I don't know what the visa requirements are for you being Canadian. But I assume there are some restrictions about how long you can stay. Usually having a confirmed job allows you to stay longer, but you generally have to have documents from your employer confirming it prior to arrival.
Here's a link to the Cayman job requirements.
http://cayman.com.ky/cayman.htm
Edit: I see Walter has picked up on it also below, but I'd have to add also - Are you sure this is what you want to do? My original dive buddy - who by the way talked me into taking the cert class with him - quit one local dive trip after our checkout dive and never dove again, while I've been diving regularly since then - 1981.
A second point would be that just because you go through instructor training, I don't know how marketable a candidate you would be at a premiere dive location like Cayman with your amount of experience. There are hundreds, probably thousands of Divemasters and Instructors who would have priority over someone with your experience level in the minds of a Dive Operations Manager. They have to have someone who has the experience to deal with the situations that might arise, especially given that a lot of the diving on Cayman is done by vacationers at the resorts who sign up for Discovery Diving or are novices. A lot of their traffic is off the cruise ships and those tend to be the once-yearly divers if that. And it's almost a given that they'll get into situations above their skill level, either out of stupidity or ignorance. An added factor is that a lot of the first dives on Cayman are deep - exceeding 100' or more is not uncommon.
I do know of one IDC in Cancun/Coz that advertises that they place a lot of their graduates locally, even some at their facility - it's a large place. I think it's called Aquaworld. Cancun_Mark on this board knows of it/works there.
Good luck,
Steve
No skateboarders in Cayman that I saw. Lots of kids on those little scooters though.