If you are renting out rooms and provide additional services to your tenants, such as cleaning, security, and meals, you may be carrying on a business. Report this income on a T2125 - Statement of Business Activities.
If you rent the rooms and provide basic services only, such as heat, light, parking, and laundry facilities, you are considered to have Rental Income and would report this on the T776 - Statement of Rental Income.
Here's some more information from CRA: https://bit.ly/2VsM43d