@Adam Rothweiler Sounds like your making the transition from SFR to commercial so the likely 1st purchase would be a smaller building that will likely attract mom & pop businesses.Most folks don't go from SFR to a plaza with a grocery store as the anchor.When you are screening the mom & pop businesses there is no reason not to run a credit and criminal check on the owners themselves. 

I get one low life after another with evictions, criminal histories, low income but thinks they can afford it (75% of income on rent), they are going to pay the landlord who evicted them from their first apartment three years ago back even though I have had all this time to do it and still haven't, he evicted them after their first month it wasn't their fault, I'm innocent, blah bla blah. 

It has no windows and no secondary emergency exit and is uninsurable in it's present condition.If there were a fire now and they were killed,the previous owner could be sued and maybe jailed for negligent homicide.Demanding and accepting one penny from them would make you criminally liable as well.You need to get them out asap and not accept any money from them.Don't give them anymore grief and be helpful finding them somewhere else to go.

How do you go about doing a criminal background check?

I explained that the new roommate would have to apply ($30) as we needed to do a criminal background check.  

Saw the documents in the house that this person is a criminal, has been in Jail in Louisiana and has been doing illegal business and sale stolen cars. 

Be sure to look at past evictions, credit, and criminal for every applicant.  

That's an excellent question that you need a local real estate lawyer (not a divorce lawyer, not a criminal defense lawyer, a real estate lawyer) to answer after they have reviewed the contract.

In America, small business is being increasingly looked upon as a criminal behavior by both the public and governments and our society is extremely litigious. 

We just did the research on these new HUD guidelines the other day and here's a snippet of the larger article:What HUD’s new Guidance means for housing providers:Arrests records are not a valid reason to deny a rental applicant housing.Convicted criminals may be denied housing if the reason for their convictions clearly demonstrates that the safety of your residents and/or property are at risk.Blanket terms in your screening criteria that say “Any criminal convictions will be denied” are now considered discriminatory and in violation of the Fair Housing Act.The new Guidance does not make criminals a protected class, but rather establishes requirements to clearly prove why you are denying an applicant based on a criminal conviction.Remember that a housing provider violates the Fair Housing Act when the provider’s policy or practice has an unjustified discriminatory effect, even when the provider had no intent to discriminate.source and full article