[NE] Question about a possible employee in Canada

We're looking at a finalist candidate who "is Canadian". That's all I've been told for the moment.

I'm assuming they've stated they're legally authorized to work in the US (and that will be verified, obviously). That's all I know right now (no idea if they are living in Canada or the US).

What if they live in Canada? What do I need to know? Been doing this almost 20 years but have zero international experience.

What if they live here but want to take a trip back home and work from Canada for a while?