According to Citizenship and Immigration Canada, the cost of sponsoring a family of four (two adults and two dependants) are estimated at $26,000. That includes:
$20,000 income support for 1 year
$1,150: Basic clothing allowance: $325 per adult; $250 per child
$600: Winter clothing
$2,945: Basic furnishings, linens, household products, etc.
$400: Food staples
$300: School supplies and fees for K-12.