Hey Olivia! Congrats on choosing McMaster, and welcome to the MacInsiders community
Those accepted to McMaster who meet the Residence Admissions cut-off average (82%* for the 2014-2015 Academic Year) are guaranteed a residence space provided they meet the application and deposit deadlines.
If you're below that threshold and aren't guaranteed a spot in residence, then it all comes down to what your average is. If you have a higher average, you get a higher spot on the waiting list. It'll become more clear once people start to see their positions on the list and start posting them on MacInsiders you'll get an idea where you stand and get a better idea of how many people are on the list ahead of you. If you're really low on the waiting list then you should start looking at off-campus housing options then.
But right now it's pretty early to tell.