There are circumstances in Ontario, mostly relating to trying to terminate tenancy, where the landlord can't reasonably refuse a request to sublet the place. I believe the intent is that you don't get trapped in some lease when you've lost your job and have to move cross-country. The landlord is obligated to mitigate losses, and subletting covers that.

I'm going to assume "temporarily leasing my place to make $3,000" won't qualify, but I'm no lawyer. There are liability issues associated with people subletting, and I'm doubtful AirBnB has all those bases covered.