The common denominator in demonic possession of a person can be found in the end result of the victim: death! The sole purpose of a demon when they possess a human being is to destroy that which God loves, first and foremost. The second biggest reason is to cause torment, fear and confusion. Not only to the victim, but to the victims' loved ones. Imagine watching someone you love going in and out of reality, for weeks, months or years on end. Another reason for demonic possession of a human is to sabotage Gods plan for the victims life. Can a Christian become possessed by a demon? Yes!
It is not a matter of faith or the lack of it which allows a demon to enter a human, but rather openings in our defenses. We are sinners, born into sin. Because of that fact, we sin every day. For us as mortal beings to suggest that a Christian cannot be possessed by an evil spirit is akin to elevating ourselves, upon receiving our salvation, to the level of Jesus Christ. If we are born into sin, we can never attain Christs' level. So, therefore, anyone can be possessed by a demon!
The stronger you are in your walk with Jesus the less likely you are to be possessed. But at the same time, if your walk is strong with Jesus, you will be watched intently for openings to possession. Demons will use things like pornography, drugs, alcohol, pride and greed (to name a few). They use whatever they either already know about you from your past or what they are learning about you right now. They send a fleeting immoral thought about the person you saw today at the store. Innocent enough, but the seed has been planted if you do not recognize the sinful nature of that thought and repent of it.
Once the seed is planted it is like a cancer that grows unchecked. A person can end up completely taken over before they realize what has happened. If they don't get help they can end up doing the devils work. These can include things like molestation, rape, incest, murder, mass murder, serial killing, spree shootings, fratricide, ethnic cleansing. Lawlessness accomplishes two things for a demon in possession of a human -- in the body he has taken over he can spread demoralizing fear and the eventual capture or death of the victim.
With a house, things are a little different. Although the end result can be the eventual possession of a human living in the house, the operations that a demon takes part in while possessing a home are the same as possessing a human (i.e. torment, fear and confusion). When they enter a house they can be there a very long time and go completely undetected. Other times its like a circus set up camp in your living room! Each demon is different in how it operates and some will adapt to find the fears or weaknesses of the people living in the house they have entered.
Once again it is a game of cat and mouse. The demons aren't in a house to rattle chains and produce ghostly apparitions. They are there to find a way into your life, to influence you in small ways at first, to find a crack in your armor. Then they will try to rip the armor off of you and leave you exposed. Demons have no right to a Christians home except that which we as sinners give to them. Whether we know it or not, we invite them into our lives at some level every day.
But now armed with that knowledge, will you do nothing and be slowly taken over?
Or will you stand up to that which cannot harm you, knowing that God is your armor?
Turn to Jesus every day and he will protect you from them. If you do not know Jesus yet,
please come to know him right now! If you live another twenty years on this earth, I believe that sometime with in those next twenty years we will witness every knee bowed! Praise His name.