It looks like you can grab one time purchase. https://www.amazon.ca/dp/B07FTLRGCM?tag=pcp0f-20&linkCode=ogi&th=1
Looks to have Word, Excel, Outlook, and Powerpoint for around 320 CA dollars.
Normal 1 year sub is around 79CAD Yearly and 8CAD per month https://products.office.com/en-ca/compare-all-microsoft-office-products?&activetab=tab%3aprimaryr1
If they come out with a new version within 4 years and you get it you'll have payed like 4 dollars less than if you had just gotten the yearly sub. if you go month to month you'll have payed more.