Having only a work permit would be an instant no from any bank or mortgage company, you need your Permanent Residency.
With a work permit, you can probably get a credit card and start building your credit rating (depends on the bank, some do some dont, but i know a friend with a work permit and an RBC Visa, other banks like Scotia will only give you a secured Visa).
Also you need a downpayment, so you need to save money. Unless you go for Rent to Own with zero down, which i think they are a bad choice for desperate people.
Also, house prices are going down right now, so unless you have a juicy downpayment (say 20% for a 300,000 home, so $60,000) and a knowledge of the possibility that you might lose some money, then i would say you wait until you have the money and the residency.