Based on Marc’s criminal background I wouldn’t want the liability of him managing my tenant relationships. 

Could be a bag of weed inside, or could be a den of armed criminals... they don't know.

—In all criminal cases, contempt cases, and other cases filed pursuant to this chapter, if a party has sold, leased, or let real estate, the title to which was not in the party when it was offered for sale, lease, or letting, or such party has maintained an office bearing signs that real estate is for sale, lease, or rental thereat, or has advertised real estate for sale, lease, or rental, generally, or describing property, the title to which was not in such party at the time, it shall be a presumption that such party was acting or attempting to act as a real estate broker, and the burden of proof shall be upon him or her to show that he or she was not acting or attempting to act as a broker or sales associate.

Apart from those people with guns who also HAVE a criminal record (and most probably own the gun illegally) it wouldn't do any good with respect to incidents related to guns.

Spend a few weeks and just a few thousand bucks to get your license and save from stress and potential for criminal defense legal fees.

Instead, it's always about things like poor service, failure to take or return phone calls on a timely basis, high tenant turnover, excessive maintenance costs, slow payment of owner dispursements, lack of timely financial reports, high monthly maintenance reserves, and even suspected criminal activity.Investors are typically unaware or simply dont care about license law as it pertains to their PM, until the guy walks off with the rent money... or ignores problems until the owner is called into housing court.It seems that otherwise good PM companies have a dropoff of service and responsiveness when they grow too fast.I know of one local PM who is recommended by a local turn-key provider.

...on the other hand, a drug dealing, criminal scumbag tenant-from-hell occupying the property often gives you the leverage to buy at a GREAT PRICE.

Unless you are concerned about a criminal type of background, I would not even bother for her.

Screening revealed no prior history of domestic violence, or any serious criminal history for either.About 2 months ago I started receiving reports from one of their neighbors that the couple was arguing, and that he was acting irrationally when angry.  

Health problems,deaths,criminal charges, loss of home values..