From Nova Scotia but I currently live in PEI. Anticipate that groceries, gas and similar things will likely be more expensive here than you're used to as they need to be trucked onto the island. Average rent is about 1200-1500ish for a 1 bedroom and 1800-2000ish for a 2 bedroom I believe (haven't looked in a while so don't 100% quote me on that). It is excruciatingly expensive to fly out of PEI but it also costs $50 to leave the island by the bridge, so you might want to consider that if you plan to travel frequently.
Because we have the AVC, the demand for vets directly in Charlottetown especially is generally a little bit lower than in other provinces, though I'm sure finding a job wouldn't be too much of an issue. May have to accept going a bit outside of the city though. The average salary for a small animal vet depends on many factors but I'd anticipate somewhere between 70k-100k?
There may be someone who is out of school and practicing in PEI on this forum who can better give advice on the job outlook.
I would prepare for a bit of a culture shock (depending on where you're coming from). Some Americans I've talked to have struggled with our slower pace of life in the Maritimes, and how many things get shut down throughout the winter.