Generally speaking, any revenue received for renting out a portion of your house would be taxable. The only exception to this would be nominal amounts from family members to offset some of the cost of maintaining that same family member.
If for example you rent out your basement or a couple rooms to borders, you have to report that income for tax. You may however, also deduct a portion of your property expenses such as mortgage interest, utilities, property taxes, insurance and maintenance against that income. The amount deductible would be relative to the square footage of the portion of the house rented against the total square footage of the house. Direct expenses relating to the area rented may be fully deductible. You may also deduct depreciation (CCA) as an expense. It is not generally recommended that you do this. Deducting CCA eliminates the tax free gain on sale of a principal residence. Ordinarily, a gain on the sale of a principal residence is not taxable. Upon deducting CCA for rental property or business purposes, you lose this benefit. For the small amount of deduction, you may get on an annual basis for a CCA claim, it is not normally worth the high tax cost on eventual sale.