It will feel like a mistake very fast. 

To be honest I realized yesterday that when doing my calculations I made a mistake; since I’m buying the duplex as a primary and I must live in it for a year, therefore I’ll have to pay utilities.

Even if FSBO folks make a mistake, I doubt very highly it will be anywhere near that amount of money. 

Always a mistake IMHO.

Your first problem, and mistake, is you don't know your market. 

You need to always know what you're spending $$ on so you don't keep making the same mistakes.

Any pro tips / mistakes to avoid before I leave and fill the space with a new tenant?

I learned the importance of concentrating on facts and avoiding making the same mistakes by thinking back on my previous experiences.You must put logic above emotion if you want to be a successful real estate investor.

However, two oversights have affected my calculations: (Both dumb mistakes I can only blame myself for)Higher-than-expected property taxes and municipal fees in University Heights compared to Cleveland proper.Overly optimistic rental income estimates.After adjusting for these factors, including property management costs and other expenses, the revised cash-on-cash return is about $12,000 annually, slightly over 5%.

@LaShanti Penn one of the biggest mistakes owners make is not understanding the different risks with different Property Classes.They often look at cheaper properties that are Class C, but expect Class A results.Recommend you first figure out the property Class you want to invest in, THEN figure out the corresponding location to invest in.When investing in areas they don’t really know, investors should research the different property Class submarkets.