Drugs, registered sex offenders (7 on that side of the freeway), gang affiliates, etc. are all nearby. 

With my smaller apts, I post in the ad that we follow HUD occupancy guidelines: 2 per bedroom max, kids of opposite sex over 2 yrs need their  own bedroom as well.  

For some reason, it is where all the felons and sex criminals live. 

I have a property across the street from a sex offender and I told my sister, a probation officer, what he served time for which was indecency with minor or some such and she said what he did was likely worse but he plead it down.

This criteria is just based on risk and not race, religion age or sex.

The reason you can exclude convicted sex offenders from parks is because society has decided that we do not want individuals with a high recidivism rate around our kids. 

I remember a time where the same type of questions were written about blacks, Hispanics and same sex couples.

Sort of like "If you only score one out of ten times you hit on members of your preferred sex, your standards are too high or you are not swinging enough".You can throw a random 50% offer at every property that comes on the market and sure you may get one out of fifty.

The full credit report, criminal/sex offender search, eviction search and bankruptcy search all come directly from the credit bureau. 

What some people call "marriage" others might call "sex for comps."