SOLD!
With the early termination fees, first month's service and setup charge, you'd probably spend as much or more for the Sprint iPhone as you would buying an unlocked Canadian iPhone, wouldn't you? Why go through the hassle?
Now, when you're ready to sell a Sprint/Verizon iPhone 4S, I can see making more selling it as unlocked to non-US buyers. But that's a while down the road.
Basically I won't be returning to Canada for a year (and iPhone prices are 40% more here), so I have this great opportunity to get an "unlocked" Sprint 4S from the US in two weeks.
I didn't know you still had to sign a contract to get the phone though, that makes things a little more complicated, as I don't want to have to ask my friend to sign a contract with her credit card and then try to cancel it the next day - I had assumed you could just buy it outright like at the Apple store...