Probably nothing. The last time I was there (early 1990s) there was just a guy sitting behind a raised desk as you walked through. Now, if he had a bad feeling about you, you would probably get taken aside. And I don’t know, but it would probably be the same questions as going between Canada and the US: business/pleasure, length of stay, do you have relatives here/there, and maybe questions to establish your permanency in your country of origin. Just be calm and truthful and you will be fine. :c)