His trial at Carlisle Crown Court heard that one of his victims complained to police about him persistently harassing her in 2008, three years before his arrest.
During that time he continued his pattern of behaviour in what the prosecution described as a "cold, clinical exploitation of the desperate and vulnerable".
His mode of operation was to target girls and women who he thought would rather have sex for money than risk jail by stealing to feed addictions to drugs or drink.
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Marjorie and Michael Cawdery, both 83, are understood to have been stabbed to death in a killing their family called "incomprehensible".
Detectives have launched a murder investigation following the shooting in Brent, north west London on Friday night.
Hot and humid throughout the Bank Holiday Weekend.