R.K.
Any paranormal activity can come from a variety of sources. The land your house sits on may have been a vacant lot or farm land for 100 years before your house was built but ... it may have been a native burial ground or village or battle 100-200 + years before you house was built. If you purchase used furniture it could have been a favorite peice from someone who passed and the family sold off the peice after they passed and that person comes back to sit on it again. So a rocking chair will rock when 'no one' is there. A radio will suddenly turn on-even unplugged.
I am a psychic/medium and sometimes spirits will follow me home because I know they are there. Sometimes they have jumped into my car as I am driving or will call out to me as I drive past. They can be persistant little buggers.
One thing to remember -- demons do exist -- sometimes we see them as children and think they are ghosts of children. They can appear to be harmless but always be wary of child ghosts.