Yes, a purchase contract with specific language for the option credit, written or reviewed by a lawyer licensed in that province and familiar with RTO, such as Barry McGuire. Also, read Mark Loefflers book on RTO. Ensure that you have TWO contracts before you start, one being the lease and the other being the option to purchase, reviewed for the province as the chance is around 50% that tenant-buyer will default before purchase. Hopefully deposit is big enough to cover property damage and multi-month vacancies and eviction process !