Ms Gallagher was responding to news that developers have bought two Mr Fluffy properties in the past two weeks – one at 13 Allan Place, Curtin, which sold at auction last Saturday, and the other at 8 Bateman Street in Kambah. Both are in the RZ2 zone, which allows multi-unit development depending on the block size. In both cases, it appears the developers are planning to pay for demolition and remediation themselves.

Ms Gallagher said people were free to go ahead and do their own remediation, but they would not be part of a government scheme.

"My bottom line is I don't want any opportunist to come in and expect that we are going to be taken for a ride on any of this," she said.

She did not rule out a compulsory buyback of Mr Fluffy houses. But she also wants flexibility, including for people who decided to demolish, remediate and rebuild their own homes.

"There will need to be some flexibility around it because there is every different set of circumstances and permutation you can believe is involved in this," she said. "There's elderly people with early onset dementia who are in aged-care facilities now because no carer will care for them [in a contaminated home], there's young couples that are mortgaged to the hilt and lost money on the house."

She said the desire of some owners to stay on their blocks had been "factored into our consideration", but would depend on the Commonwealth's response.

"We have to try and minimise the net costs of the scheme and part of that is recognising value in the land," she said. "If we're going to buy back homes we're going to have to do it in a way that minimises the impact on taxpayers."

The ACT government estimates a $300 million net cost after it sold off the cleaned land.

Real Estate Institute of the ACT president Ron Bell expected a compulsory buyback, with people forced to compete on the open market, even at auction in prime locations, if they wanted their land back.

"I know a few people that don't want to move but I would think if the government go down the path of acquisition they will simply take it and remediate the land and sell it, because they would have paid the people out," he said.

Ms Gallagher confirmed the possibility was part of the mix.

Asked about ongoing Mr Fluffy sales despite the uncertainty, Ms Gallagher said the government could not stop people selling. But sellers ran the risk of not being involved in any government program.

She ruled out paying market value to new buyers who have bought a Mr Fluffy home at a discount, knowing it was a Mr Fluffy.

The government was determined to ensure it was not taken "for a ride" and the scheme was both affordable and flexible. "And that is going to be hard because you don't want it so flexible that everyone just runs a truck through whatever process you put in place so you've got 1000 different responses."

Mr Bell said it was "right and proper" that people buying Mr Fluffy homes now should only get back what they paid, minus the stamp duty. He was "at a total loss" to understand why people would buy Mr Fluffy homes, given the imminent announcement about a buyback and demolition scheme. He understood why people were still trying to sell, to get out and get on with their lives, but he urged them to consider waiting for the announcement.

The impact of 1000 buyers looking for new homes would have a huge impact on the local real-estate market, he said, with only 2400 houses on the market at the moment, 1000 fewer than this time last year. The demand could push up prices.

The construction industry says the scale of the demolition and rebuild would be bigger than experienced after the Canberra bushfires, and a boost for the industry and economy.

The Curtin home, openly marketed as a Mr Fluffy home with people prevented from entering the property, sold to a developer for $570,000, which was above the land value of $450,000 but $55,000 less than what the sellers paid for it in 2010.

The Kambah home had sold for $480,000 – almost $200,000 over land value.

Peter Blackshaw Tuggeranong principal Robert Peaker said developers would still get a margin after paying demolition and remediation.

He had a handful of Mr Fluffy home owners who were waiting on a decision from the government before listing their properties.

LJ Hooker Manuka principal Stephen Thompson said the Curtin sale could be an incentive to other Mr Fluffy owners to sell, with another RZ2 zoned home in Farrer about to be listed and marketed as a buyer beware.

Mr Bell expected the buyback and demolition to take four or five years.