http://www.cmhc-schl.gc.ca/en/co/reho/yogureho/fore/replli/replli_004.cfm
Depending on where you rent, the allowable deposit varies. In most jurisdictions, landlords can ask for a security deposit, which is usually equal to the last month's rent. In Ontario, however, landlords can only ask for a rent deposit and they cannot use this amount to cover damage to the premises. In Quebec, the landlord cannot ask for a deposit. Check the Provincial and Territorial Fact Sheets for province-specific information on what a landlord can legally require from new tenants.