Every adult must be screened and approved, period.Here's a detailed guide on how to screen applicants: Application Screening Guide

In terms of other factors, I'm not sure there's a lot because I did have some people express interest in filling out an application before, and I actually got really close with one potential tenant, but it was because of the alcohol policy that he ultimately decided to back out.

Not sure how many PMCs you've had bad experiences with, but we'll take exception to:"Then do a thorough research on tenant applicants (note: leaving this to a PM may be hazardous to your financial health)".BP seems to have more threads about screening mistakes by DIY landlords as opposed to PMCs.Now, if you'd have mentioned Maintenance, you'd get no argument from me:) Even the PMC industry acknowledges maintenance as one of the biggest challenges.Rereading my post, I kinda see how I sounded negative toward PMs.  

How many applicants did you interview?

Maintenance at at PM company or one of the big hedge owners like AH4R, leasing at apartment complex will teach you a lot about applications, fraud, leases, collections, evictions. 

The city made me conform to their exact permit application process which was burdensome and frustrating.

You will be asked to disclose this during the application process, and not doing so is concealing a debt and would be fraud. 

@Joe Norman Those were the big 3 I figured would help the most, but I think wasn't sure how much actual applicability they had as a business owner/investor.

Piling on...all occupants who are 18 or older (or legal emancipated minor) should absolutely be required to make application. 

.✅ Professional Tenant Screening – Property managers have systems in place to screen applicants thoroughly, reducing the risk of bad tenants.✅ Knowledge of Chicago Rental Laws – A good property manager stays up to date on local laws, helping you avoid costly legal mistakes.✅ Maintenance & Repairs Handled – No more emergency calls at 2 AM about a broken water heater!