Mohammed Iqbal spent almost a month bullying, attacking and humiliating the man in his own Wakefield flat after he built up drug debts.
Iqbal, 19, was handed a 12-year sentence at Leeds Crown Court for the vile treatment of the man between April and May of last year.
He had denied the offences but was found guilty after a trial in February.
The court heard that Iqbal took advantage of the man, who was diagnosed with severe mental problems, after selling him drugs.
The man, who cannot be named for legal reasons, racked up debts which he could not afford to pay back.
The judge, Recorder Jeremy Hill-Baker, told Iqbal: "What followed was a persistent course of conduct by you whereby you manipulated and severely bullied him."
Iqbal, of St Catherine Street, Wakefield, made the man drive him around so Iqbal could make cash collections.
The court was told that Iqbal would assault the man if he did not meet his required standards.
The teenager kept hold of the man's bank card and spent his money as his own, limiting the victim with how much money he had to spend.
He also fitted a padlock to an internal door of his home and kept him out of rooms.
Recorder Hill-Baker said: "You assaulted him repeatedly with a number of weapons, causing him multiple bruising and burnt him with a lit cigarette.
"You further humiliated him by sexually abusing him. He lived in fear of the assaults."
The court heard that Iqbal forced the man to perform a sex act on two occasions and sexually assaulted him with a vacuum cleaner.
He also threatened to give crack cocaine to the man's son if he reported the abuse to the police.
The victim first spoke of the sickening attacks after his mental health worker raised questions about his injuries, but was so terrified that he gave a false story. It was only after he was moved from his flat that he finally broke his silence.
A victim impact statement said the man was still suffering from nightmares, is scared to go out and is terrified of seeing Iqbal again.
Iqbal was found guilty of sexual assault, causing a person to engage in sexual activity without consent, holding a person in slavery or servitude, two counts of actual bodily harm and attempted assault by penetration.
He appeared for sentencing via video link from HMP Doncaster, where he had been held on remand.
Paul Addison, mitigating, said: "There's nothing I can add, to be frank, about this. He continues to deny the allegations, therefore my hands are tied to what I can say."
He added that Iqbal's young age and lack of previous convictions were the only real mitigating factors.
Recorder Hill-Baker told Iqbal: "It was clear he was a vulnerable and frightened man very much in fear of you who abused him in his own home.
"It was not a single offence, it was a course of conduct, and I have come to the conclusion you are a dangerous offender."
He handed him a 12-year sentence, made up of 10 years in prison with an extended licence period of two years.
Iqbal was also made the subject of a restraining order of indeterminate length to keep him away from the victim and must sign the sex offenders register for life.
Detective Inspector Kristy Wright, of Wakefield District Safeguarding Unit, said: “This was a harrowing time for the victim who was exploited and living in fear for over a month through no fault of his own.
“Iqbal took advantage of someone who was vulnerable and deprived him of his basic rights.
"When officers found the victim, he had been beaten black and blue, and he was too afraid to speak to us through fear of repercussions.
"I’d like to applaud him on his bravery for speaking out and sharing his experience, which has led to this great result today.
“No-one deserves to live in such conditions. We worked hard with partner agencies to safeguard this victim and are ready to help anyone who is a victim of this type of crime.
“This is the first conviction of this nature in Wakefield, and we hope this serves as a stern warning that we will pursue those responsible and bring them to justice.”
This article was first published by the Wakefield Express.