Here's a link to CMHC's guidelines:
http://www.cmhc-schl.gc.ca/en/hoficl...e-03-27-09.pdf
Down payments can come from borrowed sources provided it is between a 5% and 10% down payment.
(Page 2 under downpayments)
If you are borrowing funds to get to that magic 20% mark then it isn't CMHC guidelines you are worried about it is the lenders. A lot of lenders will allow you to borrow the down payment provided the additional debt load you are taking on does not screw up the debt ratios.