These agreements allow people to stay in their homes as tenants
Two families have warned of the dangers of entering into sale-and-rent-back property agreements.
They sold their houses in south Wales to a company called Home Assured Limited but were left homeless.
The families wanted to continue living in the properties as tenants but the houses were repossessed.
Trading Standards officers in Reading, where Home Assured is based, said they were investigating. Home Assured was not available for comment.
Mike Talbot and his wife decided to sell their five-bedroomed house and rent it back after seeing an advert for Home Assured Limited in a newspaper.
The couple, who wanted to downsize, sold their home and signed a tenancy agreement to rent it back for a year while they looked for a new house.
But after six months, Mr Talbot received a letter telling him the property had been repossessed.
"It's devastating. We had lived in the house since the year 2000 when we initially bought it," he told BBC Radio Wales.
"We had looked after it and it was a lovely house, a five-bedroomed semi-detached house.
"We lost a lot of sleep and worry over it."
Mr Talbot was paid some money for the house but said he was still owed £18,000 and disputed the £27,000 worth of fees the company deducted.
Sale-and-rent-back schemes work by allowing home owners to sell their property to a company which pays-off the mortgage.
The former owner then continues living in the property as a tenant.
These schemes are designed to help those in financial trouble to stay in their homes, but home owners will often receive less than the market value for their property.
Shelter Cymru and Citizens' Advice Bureau said some people entering into these agreements had received between 20% and 60% below the actual value.
There are also fees and a percentage of the sale will often be kept by the company until the tenant leaves or decides to buy the house back.
Tenants in such schemes have few rights as companies can sell the property during the tenancy agreement, even without telling the tenant.
A woman, who did not wish to be identified, was left homeless after selling her four-bedroomed home to downsize.
She said she was owed more than £23,000 by Home Assured and also disputed the £27,000 fee.
"We've gone from owning a four double-bedroomed cottage to being rehoused in a two-bed council flat," she said.
"I can't drive past there [her former house] because it's painful.
"In the beginning, I know its sounds stupid, I blamed the house. I felt that the house had let me down.
"I had given that house so much for 12 years and I still call it my house."
The BBC tried to contact Home Assured's company director Philip Hope via the firm's website, telephone numbers and several mobile phone numbers but received no response.