Do some research on antisocial personality disorder, which is closely linked with sociopathy and psychopathy. The number one, defining characteristic of a psychopath is exactly what you describe - a complete lack of empathy. Also relevant is the ability to form close/loving relationships with others. Especially relevant is your description of how all you could think of was how you could personally benefit from your neighbour's trust in his time of need - very predatory.

Psychopaths are "wired" differently from non-psychopaths - they see how other people have relationships of a type they can never hope to understand. Being a psychopath is not necessarily as Hollywood portrays it - you're not like Hannibal Lector and you're not going to start chopping people up. Hopefully not, anyway. But you definitely sound like a textbook psychopath to me.