A Sublease Agreement is a contract that outlines the terms of a sublease between an existing tenant and a subtenant. A sublease agreement is a legal document that allows a tenant to sublet a property to someone else (subtenant).Also known as subletting. How do I fill this out? Set out fair and legally binding terms as you lease your Ontario premises. Cover crucial aspects with our Sublease Agreement Sample Ontario template. As title suggests, I will be subletting my room in a 2 BD 1 BA in a purpose-built rental. Not sure how to draw a contract:.