The reason for the background check is I would like to know who I have living on my property, sexual predators, past criminals, I want to know.They are actually considerably below market rents for their unit and the area, I mean like $500 dollars a month below average.  

Wait, no I don't; I'm now an <intelligent> R.E. investor who has self discipline and can delay gratification.  

You are looking at it from the immediate gratification vs. long-term gratification of being able to retire at a young age.

To be a good investor you need to: Be self-motivated to work hard (this can be proven by earning a good income)Have basic accounting skills and ability to follow the money (this can be proven by setting and staying within your monthly budget)Live below your means (this can be proven by setting aside a little $ each month for investing)Be responsible and keep up with things (this can be proven by paying your bills on time)Lastly but certainly not least, delay gratification (this can be proven by not cannibalizing your investment savings when circumstances of life tempt you to do so).

There is a park in my area that will not rent to sexual offenders.  

For someone truly looking for bigger pockets ; ) and isn't afraid of delayed gratification and huge learning curves, what would be a good niche to begin exploring?

Immediate gratification is not part of RE investing.     

When 1 out of 4 girls & 1 out of 6 boys are sexually assaulted by their 18th birthday, there are a TON more sex offenders out there than what state websites show, because most are never caught & convicted. 

My wife volunteers at a women's crisis center that deals with sexual violence.

You didn't make the choice to borrower from your future self in order to have gratification now.