Whew. You know, I have to admit, as far as 'reasons for a house to be haunted' go, I think 'it was built with the money of a predatory loan shark' is. Kind of genius. Like every single yen that went into that house was probably skimmed from human suffering, from the most vulnerable of society. Even before the use of the well.... it'd already be evil enough.
I like how the parents kind of. Float uncertainly in between being haunted or not. Like a walking dream.