... there were a protagonist that was motivated to murder homeless people. But, to do it, he would talk them into a kind of depression and then give them a large enough sum of cash that they would use it to deliberately overdose.
I'm sensing a theme of money and power and also the power of words and ideas. The combination of the two (money and influence) might say something about Big Media? Maybe?
The idea is pretty raw at this stage. But, it feels like it is worth writing it to find out what happens.