You would have to look in your local classifieds, Airbnb or call a realtor as to what would be the going rate for a room in your neighborhood.
Since you mentioned your uncle with this Fair Rental Value question, here's some info that might be appropriate to your situation. Please feel free to post any additional details or questions in the comment section.
If you two are merely cohabiting and splitting the rent as opposed to having a landlord/tenant relationship, you may have a cost-sharing situation
Cost Sharing
You may have questions about whether or not you should claim rental income received from relatives or friends that live with you, and whether or not you can also claim rental expenses. This depends on the type of rental agreement you have with the tenant. Think of cost sharing as charging your relative/tenant a small amount per month to help with groceries, utilities, or general household upkeep. The amount charged would be far less than market value for the rental on the open market. In cases like this, you would not report the income from the cost-sharing, but you also would not be allowed to claim any rental expenses.
In Cost-Sharing arrangements, the Property owner cannot claim a Rental Loss. If you lose money because you are renting a property to a relative for a lower rate than you would rent it to other tenants, you cannot claim a rental loss. When your rental expenses are consistently more than your rental income, you may not be allowed to claim a rental loss because your rental operation is not considered to be a source of income.
However, you can claim a rental loss if you are renting the property to a relative for the same rate as you would charge other tenants and you reasonably expect to make a profit. In cost-sharing situations like this, the tenant will not be able to claim any tax benefit from Rent paid, or any of the Rental tax breaks provided, such as a portion of the Ontario Trillium Benefit.
If you charge a tenant fair market value for the rental and expect to make some form of profit, you should report all rental income received, and you claim rental expenses consistent with the nature of the rental arrangement.
