How is he going to reside with you in Canada for 12 months? He would need a work/study permit for the time he spends… A standard visitor visa won't cut it. The max any US Citizen can stay in Canada at one time is 6 months, unless there's a pretty good reason otherwise, and an even better reason that he's going to leave after that period of time. Additionally, the border may ask him for proof of residence in the USA. If he has a job just on the other side of the border, and were to commute every day, then he could likely change his residence to Canada without any kind of permits for the 12-month period required, and just go back and forth every day, but I'm not sure how that works exactly.
I'd just get married. Even if it's just legally at a courthouse without a big ceremony. Sponsoring someone into Canada is a pretty huge commitment anyway, 2+ years (depending on the province) of liability for your spouse should they go on social assistance, even if you're no longer in any kind of relationship together.