The 85-year-old male victim had bladder issues and investigators say Miller stopped giving the man water.
Earlier this week, the victim was so dehydrated, his body shut down and paramedics were called.
As Temple University Hospital nurses tried to treat the barely coherent victim, he yelled out, "Don't hit me again!"
Police were quickly contacted.
"Seniors should be able to reach that point in life where they are able to enjoy it not be subject to any type of abuse of this nature," said Lt. John Stanford, Philadelphia Police.
Lt. Stanford says the victims took a homeless Miller into their home in 2009.
He agreed to help them with household chores for a room. Two years later the beatings allegedly began.
Investigators say the male victim was beaten daily and the female victim was beaten monthly.
The woman told detectives that a couple of weeks ago, Miller punched her in the face several times after she wouldn't give him money.
She also says Miller said that he'd kill them if they contacted police.
Neighbors seemed stunned by the allegations. They rarely saw the victims and say Miller seemed like a nice guy.
"He told me he got paid good money to take care of those folks. He said he got paid to live there and take care of them," said Angel Corcino.
"That's sad and no one deserves to get treated like that," said Katie Corcino.
Miller is charged with attempted murder, robbery and aggravated assault.
On Friday evening, a crew put on a new door handle and lock. It's a small measure of safety after a several years of alleged torture.
"Very sad. I can imagine those people couldn't defend themselves, they were probably held hostage there," said Angel Corcino.
Philadelphia police continue to investigate.