It's now mortgage free.

Purchasing with a mortgage can increase this return to 12-18% pretty easily.

The amount my tenant is paying me per month only cover 95% of my mortgage, HOA, and taxes. 

Properties with significant equity and have a mortgage on it the mortgage company typically pays it so they do not get wiped out.

@Corwyn Oliver   If you are trying to max your cash out of the existing rental properties really the 75% loan to value is going to the max for most DSCR products and conventional lending as well assuming they are single family.

Should I create a separate management company through another LLC and pay it a standard commission, or should I operate it under the existing LLC that owns the units to avoid the complexities of setting up a new LLC structure?

Unless you want a full time job finding deal directly.For hard money / rehab financing @Paul Starnes with Investmark Mortgage For long term financing @Andrew Postell is your go to lender.

Initially, the plan was to maintain the existing tenant.

I'd go with stained or polished cement With stained they can usually add and 1/8th" or so overlay (they then stain the overlay) so any preexisting stains or anything is fine Polished cement (in my experience) is the opposite - they essentially remove 1/16-1/8" of existing cement, so surface stains will be removed but anything that has really soaked through may still remain to an extent Yes water will get trapped between the LVP and existing cement/water barrier - for this reason I would not do LVP Could go tile - but why would you when you can stain/polish it for cheaper and not worry about cracked tiles years from now when you can't get a replacement 

It sounds like you want to be a rental property owner/investor and not just looking to minimize your out of pocket housing expenses (getting a roommate to help cover your mortgage with a single family home).