Ian Knowles and Ismaila Mohamed broke into the home of 69-year-old Robert Morrison, on Grove Road, in Kings Heath, Birmingham, and viciously beat him in order to steal his bank cards, mobile phone and jewellery.
Mr Knowles suffered three fractured ribs in the attack on December 10, 2018, and was taken to hospital and discharged after three days.
However, he was taken back to hospital after being found in immense pain by police following a call from a concerned neighbour and died just three days later.
A forensic post-mortem revealed he died from pneumonia, which was contracted as a direct result of his fractured ribs, injuries sustained in the beating by Mohamed and Knowles.
Knowles was identified after police checks on the property revealed Mr Morrison had suffered a history of issues with the defendant.
Officers attended Knowles' bail hostel and during a search of the property, Knowles returned and was arrested.
Footprints recovered from the crime scene and phone analysis from Knowles’ phone later led detectives to Mohamed, who had previously lived at the same hostel as Knowles.
A key fob to Mr Morrison’s property was recovered from Mohamed’s room, alongside three watches also belonging to the victim.
Mr Morrison’s phone was also found at Knowles’ address.
Following a four-week trial, Knowles, of Waterloo Road, Smethwick, and Mohamed, of Stirling Road, Edgbaston, and both aged 20, were found guilty of murder at Birmingham Crown Court.
Knowles pleaded guilty to robbery at a previous hearing and both men are due to be sentenced on January 22.
Detective Inspector Wes Martin from the West Midlands force homicide team said: "Mr Morrison was a frail man, who used a mobility scooter, and it would have been obvious to the pair that he was vulnerable and unable to defend himself.
"Yet, this callous pair continued to rob and assault him, resulting in his tragic death."