Gas work needs a licensed technician. In Ontario, furnace and gas appliance work must be done by a technician licensed through the TSSA. Ask for their certificate.
Ask how they size the system. A proper quote for a new furnace, AC or heat pump is based on your home, not a guess. Ask how they calculated the size.
Ask about rebates. Government and utility rebates come and go, especially for heat pumps. A good contractor will know what currently applies.
Compare maintenance plans. Yearly maintenance can prevent breakdowns. Compare what’s actually included before signing up.