But isn't this your logic/rational mind kicking in? I think you're making my point that trusting gut feelings (a well-adjusted gentleman) isn't reliable, and taking some time to calmly and rationally assess the situation (the quick background check the victim's mother did for example) is a much better alternative.
You're right that being in a desperate need for a roommate, for financial reasons, may have been a major factor here. But again, psychopaths are manipulative and able to choose their victims and spot their weaknesses. Bachman may well have sensed this was a great opportunity, and pushed the right buttons (immediately writing a check).
When I was 35 I was getting divorced, and for simplicity, I moved into a shared apartment with a bunch of students (as I had to pay for the apartment with my wife, I didn't want to pay rent for two full apartments at the same time). I was a professional software Java developer at the time.
I appreciate 35 isn't 55, and I appreciate Java software developer isn't successful lawyer, but I can still see it happening even if I was older and in an even more lucrative profession. I mean people do have strange times in their lives, and not everyone is rich just because they're successful (e.g. divorce, health issues, downturn in the job market, bad decisions, etc.)
Actually that's the thing that threw me off. I mean why would a successful, well-adjusted "gentleman" even be in a situation where the best option for him is to live in a shared apartment with a woman considerably younger than him? Sure he gave her a reason, but well, he has to come up with _something_ doesn't he?
To me it seems much more likely that she agreed to him as her new room-mate out of desperate need for another person paying half of the rent.
I find the dismissal of "gut feeling" in these answers a bit ridiculous (when it comes to non-professional arrangements). Sure, you might be biased, but if you're not feeling comfortable living with someone don't move in with them!