Reasonable question.  But first look at the basics.  Immigrants have lower incomes over the past 30 years and they have at least average social support net draws.  

The study was by Grubel and Grady in 2011.  I understand that newer stats support a $30+ billion figures.  Bottom line: cheap labour is a deficit spinner.  A healthy social safety net cannot be supported on the backs of a growing pool of working poor.  Pretty obvious.

https://www.fraserinstitute.org/sites/default/files/immigration-and-the-canadian-welfare-state-2011.pdf

Cheers, 
John Meyer