As per the Canada Revenue Agency (CRA) you can deduct outlays and expenses from your proceeds of disposition when calculating your capital gain or loss. These types of expenses include fixing-up expenses, finders' fees, commissions, brokers' fees, surveyors' fees, legal fees, transfer taxes, and advertising costs.
Interest on a mortgage is deductible if you generate rental income from the property. In your case, it is deductible on line 8710 of the T776 Rental Income form.
For more information, please see the links below
Is Interest Deductible?
Tax Tip: Claiming Mortgage Interest on Your Tax Return
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