Answer:
What is neither inside the house nor outside the house but a necessity for any home?
Slayer of regrets, old and new, sought by many, found by few.
In your fire you hear me scream, creaking and whining, yet I am dead before you lay me in your hearth.
Thirty white horses on a red hill, first they champ, then they stamp, then they stand still.
Something wholly unreal, yet seems real to I. Think my friend, tell me where does it lie?
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?