Treat disabilities like you treat race, sexual orientation, sex, age, nationality, religion etc.

Why make your tenants have background checks if you're going to let them move in their boyfriends/girlfriends/friends who are violent offenders or sex offenders?

Her son who is the sex offender has a job for 1 year.

I think a cam would be obnoxious, but an interesting idea has occured to me.

In my state, that would include things like court records, criminal convictions, sex offender registration, etc. 

@DJ Roshan NNN means tenant pay taxes, insurance and maintenance which generally is defined as CAM. 

All of the details were there; toenails, fingernails, nostrils, sex organs and so forth.

I think you owe your client - especially those who are new to real estate - the duty to help them find the house that is right for them, whether it be traditional sale,Unless you are voilating Fair Housing Laws (Descrimination based on: race, color, religion, sex, handicap, familial status, and national origin; blockbusting; steering), I don't see any legal obligation to show a property or obligation to do business with a potential client.

The tenant has been registered as a sex offender for 30 years. 

Honestly the guy being a racist would probably be the thing I paid the least attention to in this situation.But sex offenders, thieves and drug dealers don't tend to advertise that in front of their house.