Typically you will require more than a 20% down payment for an investment property, unless you are planning to do owner occupied. I'd run the analysis using anywhere from 20-30% down.
Also, your vacancy is quite low. Only $88/month is only 4%, that is not realistic. Typically you'll want to set aside anywhere from 10-12%. Even if you plan to self manage, you should ALWAYS include the management fees in your analysis so your deals aren't dependent on self managing in order for the deal to work.
I see you've also set aside $260/mo for utilities. Are you sure these won't be included in the rent? Seems high to me.
You can't really make an accurate analysis until you know your total rehab costs and ARV. How do you plan to finance the rehab? If you've only seen 1 unit and estimate 10k worth in rehab costs, this could become 40k+ by the time you've seen everything and that could change the entire deal and will effect your cash on cash return drastically.
$2000/mo income on a 4 plex so rents are only $500? Either this is a pretty rough area or this property is in bad shape. Have you checked the median for the area? I recommend plugging the address into Rentomenter.com and seeing what the median is. If you plan to upgrade the units and can increase the rent a couple hundred dollars per unit it would make everything look a whole lot better.
Last piece of advice is plug these numbers in the Bigger Pockets rental property calculator so you can better manipulate the numbers and find out where it will work and where it wont.
From what I see here currently though, not a good deal.