Actually now if someone can pay me to do it, I would do it by now LOL .... this is way more profitable than chasing CF. 

Are there additional taxes to pay? 

I offer either 10% monthly and manage everything including accepting rent and paying owners, or on call management. 

Tenants pay for utilities, so for expenses I have vacancy 8% ($198), taxes $395, insurance $85, maintenance 3% ($74), CapX 5% ($124). 

The tenant is expected to notify you, and maybe they will, maybe they won't.Because they have nowhere else to go and no funds (and usually no job),  you'll be paying for an eviction. 

(Just to get back to even with selling today.)If your payment becomes $3500 and you collect $5,000 in rent with no PM charges, and everyone pays on time, and nothing breaks.

Hi all, I'm looking at some single family properties in the area and there is one for sale that says the current tenants are paying $500 below market value.

You can call it 'overpriced' but others are willing to pay it, so I'd focus on finding the best deal you can find in your area, and not on a CoC return rate that may not be realistic these days. 

We current have about $500k in equity (down payment and loan pay down).

Also, I will be paying his commission because I want these units rented asap.