Are you renting an apartment to someone else and receiving income from it?
yes, and I am also reporting this as rental income on my income tax. However, I am not running it as small business.
Here's a very informative guide from CRA on expenses the Rental Owner can deduct:
https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/rental-income/completing-form-t776-statement-real-estate-rentals/rental-expenses-you-deduct.html