As an Australian (I assume, a young enough Australian), your boyfriend is eligible to come to Canada on a working holiday visa, just as you travelled to Australia. He can work here if he gets that visa.
He is allowed to stay as long as his visa / work permit is valid. It has nothing to do with whether or not you’re married.
If you want him to stay permanently (longer than the validity of his working holiday program, or, if he gets a work permit extension after the IEC has expired, for more than a few years), you need to sponsor him.
If you will be returning to Australia sooner than that, you do not need to sponsor him.