I agree with @Eliott Elias regarding the down payment (or less if possible) as well as the 40 year amortization to help decrease the monthly amount.

And, it does Not improve your cash flow as it doesn't change your payment, it actually decreases the annual cash flow by one payment.  

The longer it takes to sell them the lower your return.The largest risk I see is a market slow down, but you are getting away from MFH so that decreases the risk a bit. 

------ My strategy is to of course increase income, decrease expenses and refinance or sell within 2-3 years. ---- But just for security, Should I try to do away with the balloon?

But...if you were to use delayed financing, then answer would be YES, it would decrease your amount of money that you receive when you go back to refinance. 

Unemployment: ideally, % is decreasing over last 5 yearsPopulation: 5-year population growth is increasingPopulation age: 5-year population age range of your target demographic is increasing Industry: ideally, no one industry is employing more than 25% to 30% of the employed populationTop employers: look up the top companies, determine what industry they are in, and calculate if that is a growing or declining industrySupply and DemandIs the supply of your product (SFRs or multifamily) increasing?

Both of my refi's required 20% equity, and even though the conventional rates are higher than the fha rates the monthly payment actually decreased since the mortgage insurance is eliminated. 

I find that increasing populations, rather than decreasing, really helps values of an investment property...). 

One of the ways my partner and I have been trying to decrease costs is doing as much of the labor ourselves as possible.

@Ruthber P check the property taxes for the building you are considering-you might be shocked.Last time I checked Riverdale property values were decreasing as real estate taxes were increasing.