Movie Pitch

This is a pitch for a low budget horror movie set in the burbs.
Billy is 15 and seems normal, if a bit moody. But he tends to wander the streets, pretending to be homeless. Kind strangers try to help. He lies and explains his single mother is abusive. His father left months before.
His plan is to have her investigated and taken away. Then he will apply for emancipation and get the house to himself, where he can periodically head down to the basement where he has imprisoned his abusive father and torture him.
There is some sort of small pet Billy will kill for the hell of it. An innocent girl will fall for his mysterious ways and be in danger.
His 68 year old grandfather is a retired detective, and not convinced his son, Billy's dad, really vanished. He goes poking around and Billy has to dispose of him. Billy hums to himself and appears distracted. He has that cute, innocent look. I see Justin Bieber as Billy.