We do not discriminate against persons because of race, color, religion, sex, handicap, familial status, national origin, age, sexual orientation, or gender identity.

Well, in CA anyway, we're required to give the Megan's Law database info in our leases, so tenants are aware of it, and can look up sex offenders on their own. 

I found one of my potential tenants was apparently dating a registered sex offender.

What if that felony that they have just been convicted of requires them to register as a sex offender?  

And was glad to see them move out :-)For instance, I routinely ignored angry voicemails from tenants about how they could hear other tenants having loud sex. 

If someone with a conviction from 10 years ago that was non-violent, and not related to drugs or a sex crime - then they are a protected class.  

I want to make sure you thoroughly understand this piece since you are going it alone.The Fair Housing Act prohibits discrimination against prospective tenants and current tenants on the basis of the following characteristics or "protected classes": race, color, religion, sex, national origin, disability, and familial status.

We use screening company to verify previous addresses, please list accurate information so we can speak to your previous landlord(s).Criminal History - No felonies, or sex offenses, drug trafficking, violent crime, terrorism, burglary, theft, arson, vandalism.

Have dinner with her at your place, watch a movie with her at your place and have sex at your place but then send her back to her parents house afterwards.  

You are correct about Baltimore and other areas in that the landlord is responsible for screening the prospective tenant for criminal record, sex offender, etc...