Things to know when buying a duplex?

[Michael Faudoa]

Hi everyone, I have a basic understanding of real estate investing but I am still completely new. I'm thinking of purchasing a duplex and I'm wondering what factors I need to consider.
Unit 1 rent is currently $1200 with room to raise
Unit 2 rent is $1250 also with room to be raised
Both units were completely rebuilt in 2016 and look brand new, modern, and great.
My mortgage PITI payment is shaping up to be $2500/mo.
Because I don't have a huge stash of cash, I would be doing 3.5% down with an FHA loan and a plan to refinance to ditch the mortgage insurance a few years down the road.

Currently, the landlord pays for water and sewer. Is it expensive to put a separate meter on each unit? 
Other than creating a budget for vacancies, repairs, and cap ex, is there any other cost of owning a duplex that I'm not thinking of? 
The post is kind of all over the place and I apologize. I'm 25 and very inexperienced, but I love this community and am curious what you all may have to say. Cheers!