OT: Rental Property Tax Implications

[Penguin]

Having trouble selling our family home in California for a move to Canada. Can someone give me some insight into the tax implications of renting ? For instance, if I sell right now I can take the equity tax free up to $500k. I have heard that if I rent for a couple of years until the market recovers I can only sell the house and pay capital gains, since it is no longer my primary residence. So does anyone know the rules which govern what is a Primary Residence ?

Thanks
Brian