Fears that desperation will force buyers to turn to "monster" of underground borrowing.
Demand for hot property has led to a multi-million-dollar nationwide the expansion of Sotheby's International Realty across New Zealand.
"You have a decision to support those who are prepared to take the risk to develop land for families."
Average new build cost in the city is $272,000 - more than Auckland, Wellington and Dunedin.
Supermarket, fast food outlet and petrol station among confirmed tenants in 1300-home North Canterbury development.