No lender advances money on an uninsured property. That makes home insurance a closing requirement in practice even though it rarely appears as a condition in the agreement, and it is the quiet reason a small number of deals fall apart late.
What makes a house hard to insure
Knob and tube wiring. Many insurers decline outright. Others require replacement within a set period after closing. Common in pre-1950 Toronto housing stock.
Aluminum wiring. Roughly 1965 to 1975. Usually insurable, but often only with a certified inspection and remediation of the connections.
Buried oil tanks. The serious one. An underground tank, or evidence of a removed one without documentation, can make a property uninsurable and carries environmental liability that outlives the sale.
Roof age. Past about twenty years, expect an insurer to want it replaced or to exclude water damage.
Galvanised or lead plumbing, and older electrical panels including Federal Pacific Stab-Lok.
The claims history of the property, and yours. Insurers share loss data. Two water claims in the last few years will follow both the address and the person.
Oil or wood heat as the primary source, and knowing whether the property has ever flooded.
Call a broker with the address the day your offer is accepted, not the week before closing. You are buying two things: confirmation the property is insurable at all, and a number. Both are useful while you can still walk away, and neither is useful afterwards.
Your lawyer needs a binder letter confirming coverage effective on the closing date, with the lender named as loss payee, usually a few days before closing. If insurance cannot be placed, the lender will not advance, and you are in breach of an agreement you cannot complete.
A home inspection is what surfaces most of the list above. See Home Inspections.