He rented to somebody who had a criminal record and income of about $1100 when rent was $825.  

Calling me a spoiled child & not an adult is a rather ignorant thing to say given you don't know a thing about me and quite frankly I find it offensive. 

The criminal report came back with several charges and arrest, however the name on the report in most places had a different suffix than our applicant (Jr vs II).

His policy is for every adult who will be living in his property to submit an application - which, upon their signature and submission, authorizes him to do background checks, criminal and rental history, credit check, etc.

I would still want to run a background check for criminal and then request an additional 45%.  

I would push to have them charged because in some places (like my state) if they are convicted damages can be awarded as part of the criminal case and collected by the court system for you.

He took offense and pulled away quickly because nothing was holding to him in writing as to why he should and was upset thinking I wanted more profit or more out of him. 

Basic terms, basic criteria, don't get yourself wrapped in things that don't make sense.Basic ,, like occupancy per unit number of people, over the age of 21,   X times 3 income for the rent, verifiable source of income, verifiable ID, credit score over XXX, criminal no felonies in past 7 years - if you can still use those guidelines, and no evictions for past X years,,.. if you verify previous landlords good luck, it's  not usually done much anymore as landlords without written authorization are usually not willing to risk saying anything, it drags the process out and with the online checks for credit and criminal it's not much a standard anymore. 

More people will take offense to your letter if you tell them that you know they aren't paying their taxes.  

Failure to do so can incur fines, loss of license, a civil lawsuit for damages and even criminal penalties.