The home where an "exploited and manipulated" 78-year-old was killed in a fire was likely to have been used as a drugs den, a report found.
Fred Payne's flat in Colchester was torched by drug addict Lisa Connelly after he took her in.
A review said Mr Payne could also have been a victim of "cuckooing" - where dealers use vulnerable people's homes.
The report also found Mr Payne was referred for safeguarding six times but had declined intervention.
Connelly, who had helped herself to a sizeable chunk of the pensioner's income before setting the flat alight in September 2016, was jailed after she admitted manslaughter and arson charges.
The Domestic Homicide Review said a neighbour at Mr Payne's funeral told a PCSO a local drugs gang had been using his flat since 2009.
It also noted possible signs of cuckooing which were missed, such as his "rehearsed" responses when challenged on his relationship with Connelly.
A urine test on Mr Payne, ordered amid suspicions he was being given drugs against his will, found no evidence of drugs, the report said.
But a GP reported that the sample may have been diluted or tampered with.
The report also found that Mr Payne had been referred for safeguarding a number of times, with the final inquiry still ongoing at the time of his death.
Financial abuse and neglect were uncovered but Mr Payne rejected offers of help, and his refusals were accepted because he had mental capacity.
The report said the housing association in charge of the flat was aware of "incidents" at the property, which were a "missed opportunity" to find ways of dealing with the situation.
The housing association said any action they could have taken would have resulted in Mr Payne's eviction.
A police review also found a number of "missed opportunities" for information-sharing.
The review said there had been "many examples of good practice" but that it was "a particularly challenging case involving an elderly man who had mental capacity and made what were considered to be unwise decisions and a woman who misused substances".