Lock used customer deposits from these contracts to fund personal or other business expenses and then failed to deliver on the deals
SFO director Julie Read said Lock showed "callous disregard for the consequences of his actions".
"Mr Lock deceived his customers and their agents," she said.
"He caused significant financial and reputational loss to his victims and in many cases personal suffering. By his deception, Mr Lock risked the reputation of an important New Zealand industry.
"His sentence also includes six months' imprisonment for providing false information to the Serious Fraud Office, which is itself a serious offence."