I didn't monitor any of my tenants until/if I got a complaint from another tenant or I just happened to observe or hear some behavior that I needed to give them a warning about.So, in my case, since I lived in the same building, if they were throwing a loud party, I'd usually see or hear it.  

@Dean Weltman I observed the same thing, those from CA were bashing the NY Post and one suggested the NY Times would be a better source.

Now I have to pay a Marshal to observe them.

Just an observation - it would require a lot of management.  

I can see, clearly, you have seen some red flags and are leaning towards not renting them.Furthermore, I sense, per my observation of this thread, a bit of anxiousness in renting out the unit quickly.

I found out that one of the tenants (family with one kid and another on the way) earns more than I do at my job (they probably make between around $45k between the two of them), and in the other unit, it's a couple with 3 kids and a dog, where the mom works full time (in a department store) and the dad goes to community college and gets stoned at home during the day (but I have no evidence of that other than personal observation when I repair stuff over there).The point is, as each week passes and I lose money paying for the loan on this property, I feel PWND.  

Just my observation and preference.    

The  kind of gains we have observed the last few years are way above the long-term 2%/yr national average -- an average that pretty much just keeps up with inflation.  

But honestly if you are happy with an expert that works in courts and legislature rather than observes in the real world, I have no reason to argue with you.

Then, can your dad go observe the place?