The complainants did not hand over any sensitive information on advice from their accountant, who told them to wait until a contract was in place.
Two days after Mr Perry first requested the information, his business partner put an offer on the business. The complainants then made the information available.
Less than a fortnight later, both Mr Perry and his business partner put in applications to drill bores on their own properties - and the following month, Mr Perry registered his own water carrying business with the Companies Office.
The offer on the complainant's business was withdrawn two days later.
The complainants allege Mr Perry had approached them "with the intent to deceive".
"He represented to us that he was the buyer. Mr Perry has been untruthful and used his position as an agent for his own personal gain."
The complainants said Mr Perry later approached them to apologise. However, Mr Perry denied admitting to pretend to buy the property.
"I called into the complainant's company to try to resolve the issue, and apologise for any misunderstandings. I deny 'admitting' that I misled or deceived them."
The Real Estate Agents Authority's complaints assessment authority concluded that, on the balance of probabilities, Mr Perry had used his position as an agent to obtain information from a client which he then used to establish his own business.
It found him guilty of unsatisfactory conduct, but found there was insufficient evidence to support the more serious charge of misconduct.
The authority fined Mr Perry $5000 and ordered him to pay $2461.40 in legal costs to the complainants.
Mr Perry's contract with Harcourts was terminated in April 2011. A decision on a complaint against another Harcourts agent, whom the business owners had complained to about Mr Perry's actions, is yet to be published.