PR stands for permanent resident, not prisoner
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When he is a PR, he is free to travel outside of Canada whenever he wants. Considering the loose requirements for keeping PR (2 out of 5 years in Canada is not very 'permanent' to me) it's obvious plenty of PRs don't live in Canada permanently.
Lots of people land with a return ticket, usually their reason for it is "I'm landing now before the visa expires, but I have to go back home soon to arrange everything for the final move". Which is a perfectly valid reason I think and I don't see why it couldn't work for you. You're just in Canada for a short while to rent a place to stay and then you're going back home to finish everything up. Or whatever. I don't think they care really.
Anyway, that's for a typical case where the sponsor is already in Canada. I guess they could make an issue of it if it's revealed you (the sponsor) aren't moving either, but I've never heard of such a thing happening during the landing.
Btw, from what I remember of my landing, nobody asked me how long I intend to stay in Canada.