Also, the fact that the listing broker factors in rental income inflation but no inflation on the expense side is another example of how unrealistic their analysis is. You must always do your own analysis of a deal, rather than trusting the listing broker's numbers. Their job is to get the most $$$ for their client (the seller).
However, what I've found, after looking at many Brooklyn multi families over the past two years, is that they don't trade like typical commercial/multi properties would in the rest of the country. More often than not you are competing with emotional home-seekers who are not doing any type of cash flow analysis. These things tend to trade based on comparable sales (comps), similar to the way single family homes sell, rather than based on cap rates etc.
Again, that doesn't mean this particular deal isn't a good investment. I happen to think you can't go wrong owning a 3-fam near Utica in Crown Heights over the medium-long term. But you will be spending a decent amount of carrying costs while you wait for the appreciation to materialize.