Hi @Kevin Rollins, by your numbers I assume you're using a conventional 20% down loan. Maybe you could speak with your bank and put down a little less? This will affect your ROI. Maybe even try to convince them to agree to sellers financing. Sometimes sellers will agree to that because they want more money in the long run, and no doubt they would make more through the interest you pay. It's worth finding out. You can find out more from @Brandon Turner's Low and No Money Down book, if you haven't read it already.
I agree with @Ben Wilkins about your maintenance and CapEx numbers. They do seem a little low but I don't know the condition of the duplex. If it were a new building, like he said, then I don't have to repeat it. If it's not new, and I'm curious no one has suggested this yet, but maybe consider sprucing the units up yourself. You can do wonders to a property by painting it, replacing carpet/buffing floors, staining or painting cabinets, etc all by yourself. None of this is outside ANYONE'S abilities, trust me on this. With YouTube, it's such a simple process, that's why you only pay $10-$15/hr for the labor. You would stretch your hard earned dollar and earn a nice return on it. You could increase the rent by $100/mo from this alone, which dramatically improves your investment. Combine this with having the renters pay for utilities and it's even better.
This brings me to my next point. Never, ever, ever be afraid of raising the rent if you feel it is justified. I'll tell you now, the renters you have now are NOT the best renters you will have. You haven't upped your experience with attracting quality tenants, and most bad tenants will be repelled through a proper tenant screening process. Truth be told, a better property will attract better tenants. Raising rents isn't a deal breaker for a lot of tenants, but if it is, you opened the door to attract a better tenant.
My last thing is this: you budgeted for property management, and that's fantastic. If you don't own any other properties, why not manage yourself for a year and collect that money? I mean still budget for it, but just pay yourself. You'll collect invaluable hands on experience and clear up some extra $$$ should any repairs be needed. Managing properties isn't difficult either. It's actually pretty simple once you know what you're doing. You can check out the Book on Managing Rental Properties, yet again by Brandon and his wife, Heather Turner, also full of invaluable information.
There's some pretty narrow-minded individuals on here that will try to give good advice, but maybe aren't the best to learn from. I would like you to re-run the numbers with all of this information and post what the new cash flow and ROI would be. Let's see if this is, in fact, a good deal or not. I look forward to the results. Good luck.
-Michael Volek