I just double checked my numbers for my duplex, it cash flows even when considering an FHA loan (I said down payment was 3.5% in the calculation) and 8% vacancy, 5% repairs, 5% maintenance, and 10% management, $40 a month for electric (2 meters are 20/mo each that I have to pay for), $33/mo for water, $62/mo insurance, $35/mo trash, and $15/mo PMI.
It's not crazy money, but it does cash flow even after all of those expenses, even though the down payment was calculated as 3.5%.
I would at least target breaking even after expenses, even with an FHA loan. I would also seek other financing options so you could put 5% down instead and not have to pay permenant PMI.
I would consider saving as much as possible right now, and probably still renting for a while instead of this option. It hardly breaks even when it's fully rented - and that's after you upped the rent. There's no upside. If a couple of things break, you have to have an electrician look at something, a plumber look at something, or you have an unexpected repair, or a few months of not having a tenant, you'll be strained financially. When it only works if everything goes right, it's not a good deal.