I have Cozy, but only one tenant uses it.

Definitely consider an option which allows you to collect rent much quicker than those others but still provides other rental management tools you might find valuable (again, not to knock Cozy or these other tools like Zillow rental manager - which admittedly is newer so they still have to iron out all of the kinks), but you can easily keep track of who paid what and on which date with a tool that is reliable and fast.

This should open up space to create a cozy living area.Upstairs I'm thinking about turning the open living area into a 3rd bedroom for maximum cash flow. 

Use COZY or some other resource to find a list of persons with evictions and then see where they were living... but maybe you need each individual's name in which case that wouldn't work. 

RentalHero, Cozy and TenantCloud seem to be the top three rental property management cloud based solutions for beginner to moderate level of landlording expertise.

Do I just go to cozy, sign up and it walks me through tenant screening and rest of the stuff.

I listed with Cozy, Zillow and Facebook rental groups in my area. 

Many others use Cozy, Zelle, ACH deposit, cash (don’t do this), and many others.

Hey @Roman Grishpul PM software Cozy should help!

Looking at Cozy, Buildium, Tenant Cloud, do any sync with bank accounts for expense tracking (trying to not do Quickbooks) I'm just setting up a simple 4-plex and I see that all of these do some level of accounting.