The proposal was that the Calders would work with Mr Lloyd on a design before buying the land and unit from him.
Mr Lloyd - who was working as a sole agent at the time but later worked for Richardsons Real Estate - prepared a memorandum of understanding (MoU) and emailed it to the Calders.
In his email, Mr Lloyd described the MoU as a document to "document past discussions, record the present and future outcomes for us both".
He suggested the Calders pay him $10,000 on the signing of the MoU.
However, Mrs Calder told the tribunal she did not like the terms of the MoU. They didn't sign it and paid him $5000.
In March 2008 the couple agreed to a design of the property and were told a resource consent had been obtained.
They entered into an agreement for sale and purchase, but differences arose between the parties and the Calders found out a resource consent had not been granted.
They cancelled the agreement in October 2008.
The couple were then sent a copy of the MoU by Mr Lloyd's lawyer, with a note that said: "You failed to make any mention in the Memorandum of Understanding signed sometime in May 2007."
A copy of the MoU was produced, which showed initials of all parties on page 2.
The Calders denied they had signed the page and in 2011 complained to the Real Estate Agents Authority (REAA).
The authority sent the document to a forensic document examiner who found the initials were probably forged.
The expert told the tribunal that under magnification pen marks could be seen where the person writing the initials had stopped and started which was very unusual on a genuine signature.
Mr Lloyd denied he had forged the documents, but said if he had he would have ensured that the agreement was signed on every page, and not just the second page.
The tribunal found Mr Lloyd forged the initials but dismissed a charge of disgraceful conduct.
No criminal charges had been laid against Mr Lloyd, and it was up to the Calders to complain to police if they wanted to, an REAA spokeswoman said.
The tribunal has asked for submissions from about the penalty Mr Lloyd will face.