I'm sure he knows a bit about criminal law. 

So, there is nothing sorted, or illegal, or "tricky" here.See this link that talks about leasing assets to a business from a CPA.Leasing Assets to Your BusinessAlso, I mean no offense by this, but sometimes CPAs don't always give the best advice when it comes to RE investments as they have 1 very narrow minded view, which doesn't always relate to the greater picture of an investor's strategy. 

Not to mention, there are potential criminal penalties.

There are a lot of programs and softwares you can use that will screen your tenants at no cost to you - the tenant will pay the rental application fee and you as the landlord will get a criminal background check and credit report etc.!

Running criminal background is an absolute must.A $12 criminal background check might have kept this killer out.I am going to point out, in the landlord's defense that it is possible that he didn't rent to this tenant.

If my response was offensive to you, it was not meant in that light.

Most of my google/bigger pockets searches are saying that you can no longer use Credit Score or some Criminal History events to deny an applicant, however most of these stories/posts are from 2019 and 2020 when the law was first introduced. 

Am I liable if there is a sex offense committed by this individual?

I'm sure opinions vary on this last point and no offense to Mil Orig but of course the loan guys want you to buy down the mortgage as that's guaranteed money in their pocket today vs.

Maybe I might get more clarity on what’s the best time to do so, and how many doors to aim to knock on per day  No offense but any investor that tells you do do door knocking is by definition ABSOLUTELY not smart.