Drinking vodka will help kill the bacteria in your throat, Marco Gastello told one of his victims before he drugged and raped her.
The 25-year-old woman had just moved into his Docklands apartment in Melbourne after seeing an advert on Gumtree.
She went to the toilet and heard the sound of a spoon clinking against a glass, as he laced her drink with a sedative.
When police searched his home over that crime, they found dozens of intimate pictures of other women and 13 child abuse videos.
Gastello, 44, an Australian citizen who was born in Peru, has pleaded guilty to five sex offences, including administering an intoxicating substance for a sexual purpose, rape and possessing child pornography.
His offending involved "serious, deviant sexual behaviour that is extremely troubling", Judge Marcus Dempsey told Melbourne's County Court during a pre-sentence hearing on Friday.
Gastello was playing pool with one of his victims, in July 2017, when she began coughing. The woman was his new housemate and had moved into his apartment that day.
He told her to drink vodka and she consumed a few shots before going to the toilet. Whilst out of the room, he added a white powder to her drink.
The woman consumed the laced beverage and stumbled to her bedroom. She awoke in Gastello's bed the next morning, later discovering he had raped her while she was unconscious.
He was arrested a few days later, with police later searching his property and discovering a pill container along with intimate photos on his devices of two other women and child abuse material.
One of the women had also just moved into Gastello's apartment when he began taking intimate photos of her while she was sleeping in May 2017, the court was told. He took more than 30 photos and stored them on SD cards.
"Emotionally the crime has torn me to pieces. Never in my life have I ever felt so isolated and alone," she said, in a statement read to court.
"What happened is still anchored inside of me."
He met the other woman at work and took 26 intimate photos of her on his phone in 2014 while she was asleep after a night of drinking. She did not discover the photos until years later.
Gastello, who has been on remand for more than two and a half years, will be sentenced as a serious sexual offender, the court was told.
Judge Dempsey ordered for him to be assessed for his risk of reoffending, as he said he was not prepared to sentence him for such "deeply disturbing sexual predation" without further information.
The hearing will continue on May 3.