Today in court his lawyer questioned the victims about the money they lost in the scheme.
Fane Ketu'u said she and her brother spent more than $31,000 painting the run-down Manurewa house they bought from Cooper. They said they replaced carpets, renovated a bathroom and fixed rotten floorboards.
Cooper's lawyer Tudor Clee asked Ms Ketu'u about a ``cash rebate'' Cooper had paid the family after the deal went through.
But Ms Ketu'u said Cooper's check bounced and she still had the original.
Judge Josephine Bouchier told Mr Clee: ``It is fair to say the idea of digging holes comes to mind and you're the one that's digging.''
Ms Ketu'u said she was asked only last week to produce receipts, and could only find $5000 worth at such short notice. However she said she could recall all the work done to the house to get it to a state where it could be rented.
She said family and friends pitched in but equipment had to be hired, and she made sure they were all fed in exchange for their labour.
Ms Ketu'u told SFO prosecutor Todd Simmonds how her elderly, sick parents overheard conversations about the family's financial position and they were worried that they could lose their family home.
"As a family this brought a lot of pressure on us and it started to divide us, so the best thing me and my brother ... We decided to move away from the family home.''
Mr Clee suggested the stress had been caused by the SFO investigation but Judge Bouchier took exception to the question.
"The witness never said that at all.''
Mr Clee also questioned Ms Ketu'u's sister, Foulata Heem-Ketu'u who said she bought two properties in Tokoroa from companies associated with Cooper but couldn't find tenants for the houses, despite getting a real-estate agent involved.
Another property was tenanted but Ms Heem-Ketu'u said Cooper was paid the rent directly and he did not pass it on.
Judge Bouchier said she found the two women completely believable.
"I find both women to be honest and hard working and they have clearly been duped by the defendant into purchasing property. Consequently they lost money.''
Cooper was involved in an incident with Kurtis Haiu in May 2011 after another property deal went sour. Haiu was discharged without conviction after he admitted striking Cooper in the face and leaving him with a black eye.
Cooper will be sentenced in August.