When the unclean spirit is gone out of a man, he walketh through dry places, seeking rest, and findeth none. Then he saith, I will return into my house from whence I came out; and when he is come, he findeth [it] empty, swept, and garnished. Then goeth he, and taketh with himself seven other spirits more wicked than himself, and they enter in and dwell there: and the last [state] of that man is worse than the first. Even so shall it be also unto this wicked generation.
Matthew 12:43-45 (KJV)
We live in a world that is full of non physical entities that are hidden to the human eyes. We are conditioned to see and to accept only that which we have reference points for and said reference points are provided by the world itself. For many the Hollywood versions of "demons" are that which they think of when they read the word. The media has done an amazing job in convincing and conditioning humanity to look for logic and reasoning and to ignore that which often is standing in front of them. Unlike the fallen angelic realms, demons are earth bound. The offspring of a fallen one with a human is a demon and as demons are earth bound and therefore not able to receive any redemption from our Creator YHWY (He did not make them, they are blasphemous by their very existence) fallen angels can and will protect their offspring.
The warnings against venturing onto forbidden planes cover demons also for it does not take much for them to set up house within a human vehicle. Many mental health problems that are often diagnosed and treated with pharmaceuticals are demonic possession, but such is the conditioning within humanity many simply believe that demonic possession is something that occurred in "past times". We are in the end of days, prophecy is unfolding and completing each moment and the veils that sat between the various realms are often very thin or even removed (our Creator YHWY promised to remove the veils between humanity and illusion in the end of days).
Demons do not require unclean homes to set up in, they do not require any special rote and ritual, there is much about the everyday human life experience that is being manifest and widely accepted within humanity to allow for demons to go about their business often in plain view. Much like the angelic realms and the new age movement there seems to be some false ideology around demons also. A demon can sit in a human church, it can attend a service and sit within a congregation, there is little to stop a demon from doing this apart from Christ. Where a minister, pastor or religious leader refuses to preach Christ there is room for darkness. Many churches and religious denominations allow the walking of demons through their rote and ritual. Where you find abominations, where you find desecration of the human vehicle, you will find demons. A robe, a dog collar or ritual robes do not protect anyone from demons. Christ and full surrender to the preaching of Christ in TRUTH will stop them in their tracks. The blood of Christ provides protection for all who are surrendered to Christ within the Salvation in TRUTH process but it is wise to avoid interaction with those who promote desecration in the first place. Immoral sexual activity, lewed and lascivious behavior, violence and aggression are all indicators that demons are present and they will seek out further hosts by pulling those who turn towards them closer to them.
Once invested in a human host demons will do all they can to keep hold of said host. Walking from a demonic path will involve surrender to Christ repeatedly as the demon goes to war with Light in an attempt at breaking the host first and foremost. There are many demons who inhabit humanity and drive addictions first and foremost, an addiction to be truly solved must involve the intervention of Christ and the full surrender to Him. Without this then the addiction will simply manifest in another form often more dangerous than the original form.