Aveo Group shares have plunged as much as 9.5 per cent in the wake of an investigation detailing claims the retirement village operator is ripping off its residents through high fees and other unfair practises.

At 1.35pm Aveo's shares had shed 29 cents to be trading at $2.76.

The fall was triggered after the publication of the first parts of a six month investigation by Fairfax Media and ABC's Four Corners has found ASX-listed retirement village group Aveo is engaged in questionable practices while raking in huge profits.

The joint investigation has spoken to current and former residents, their families, lawyers and former Aveo staff, who allege that complex contracts, crippling costs and a brutal business model is leaving them tens of thousands of dollars worse off.

Further revelations out the company's practices will be aired on ABC's Four Corners program and in Fairfax Media publications on Monday evening and Tuesday morning.

Morningstar analyst Tony Sherlock said the investigation could bring about change across the retirement village sector.

"Without being able to cross check the facts in the stories, incidents like this could be a precursor to legislative changes that could bring about a more even playing field between landlord and tenant going forward," Mr Sherlock said.

JP Morgan analyst Richard Jones said the share price fall was probably the result of reputational damage to the company as a result of the investigation.

However, he said he doubted Aveo was out of step with the sector with a range of operators charging high fees.

"It's a pretty complex subject," he said.

Aveo is valued on the stock market at almost $2 billion. In 2016 it doubled its profit to $116 million.

The majority of its profits come from exit fees, a fee unique to retirement villages.

They are calculated as a percentage of the value of the unit. In some contracts they are as high as 40 per cent after two years. On a $600,000 unit, this is equivalent to $240,000 being charged when a resident leaves the unit.

To achieve its profits, Aveo has a stated target turnover of 10 to 12 per cent of residents each year, equivalent to 1200 units changing hands a year. That turnover target is high by industry standards.

Aveo declined to be interviewed for the story but in a 19-page response to questions, which the company also released to the stock exchange on Monday, it denied it was more aggressive than other operators, denied it had a policy to churn residents.

It said its more recent contracts were simpler and gave residents more certainty about the costs of moving in and moving out.