The owner self managed and simply forgot to charge them.

One last thing, buy a couple of books on rentals and multifamily properties to educate your self. 

Hey have you thought about self managing the property?

You will be able to get answers to so many of your questions regarding real estate investing, wholesaling, flipping, rentals, lending, self-directed IRA and Solo 401k investing, or tax and legal guidance from many of the knowledgeable members.

I self manage all of them.

Walk the property and create a scoop of work for your self.

If you are self managing and your agent had experience managing or screening tenants, then if they are willing I’d ask them to teach you a way to screen them.

@Jorge Morales I agree with accounting for property management in the event you decide to move and no longer want to self-manage. 

NJ has stopped self-paced online learning now so if you do online, I think all of the current classes are still live, even if online.

in  a way many markets I see out in the mid west deep south have such huge amounts of Section 8 that that in its self is rent control cant rent for anymore than what section 8 will charge.. and with market rate rents on the collection side  in many of those neighborhoods being inconsistent  at best  kind of hold rents in check..