For an estate, sequence matters more than speed. The executor named in the will applies for probate, and title does not transfer through Information Services Corporation until that is done. A valuation can be prepared well before then and is often needed early, because the Canada Revenue Agency treats a deceased person as having disposed of their property at fair market value on the date of death.
That date of death value is a tax figure and it deserves care. It sets the cost base for any gain between death and the eventual sale, and where the estate is complex or contested, an appraisal from an Appraisal Institute of Canada member is the safer document. An agent's market opinion is the right tool for deciding whether and when to sell, and for pricing the listing itself.
For a rental, bring the leases, the rent roll and any suite permits, since income and legality both affect the number and the sale falls under The Residential Tenancies Act, 2006. Inherited houses in particular hold decades of undocumented work. Joel Dyck's hand-reviewed valuation walks the property in person, which is the only way that work gets counted.