For my next dog, pet insurance is a must. I had pet insurance on Bosley, but then decided to let it go as I considered it an "unnecessary expense". Holy cow. In retrospect, I shouldn't have let it go. Next dog - pet insurance is number one priority. It may not cover all the bills but it will certainly help. True, there were no extraordinary vet bills for the first 5 years I had him, but that last year was hard on the ol' pocket book. Yes, he was worth it, but at the same time, the pet insurance is something I'm kicking myself over. Shop around and see which insurance best suits your needs. You can get bare minimum coverage to Cadillac coverage that includes all preventative shots.
If you aren't working or have a low-paying job and have a service dog, there is help. In Ontario there is the Farley Foundation. If you do (Lord forbid) need assistance, swallow your pride and look into it. I believe it is run by the Ontario Veterinary Medical Association. I'm sure there are similar organizations in other provinces.
There is also help from your local vet. Don't be afraid to ask. In spite of big signs posted in the reception area saying no cheques accepted, my vet took cheques and not only took cheques, she took a series of post-dated cheques as well. She also cut me a LOT of slack by not charging me for several visits, and giving me serious discounts and outright freebies. Dr. Jo was a godsend. So was her receptionist, Carol-Anne. That said, if your vet doesn't help out in this way, don't get angry... they are providing a service and they are running a business. Which makes the assistance Dr. Jo gave me all the sweeter, and I appreciated it greatly. Also - don't forget to remind your vet that your dog is a service dog. You might be surprised with a discount on the total bill. For example, I got a 10% discount on the bills generated from the University of Guelph's Oncology Department. Considering just two of Bosley's bills from there came to well over $3,000, you do the math.
In the Toronto area there is Companion Animal Wellness. http://www.companionanimalwellness.com/
For the rest of Canada, you might find assistance with low-cost or free veterinary assistance and emergency pet fees assistance here:
There are other organizations out there. Ask your local vet or SPCA or Humane Society where they are. And of course, if your dog is from Dog Guides of Canada, contact them, as they would know whom to contact as well.