Am I overstating my expenses in my rental property analysis?

[Mitchell Hamilton]

As a new real estate investor, I've been leveraging the BP rental property calculator to analyze deals and I keep running into the same issue... the results of the calculator are highly unfavorable with every property I analyze. I'm starting to think I'm highly overstating my expenses and that is why I continue to see unfavorable results (specifically negative cash flow). I'm currently setting my Repairs and Maintenance expense at 10% of monthly rent, Vacancy at 6%, Cap Ex at 10% and Management Fees at 8% (the calculator advised me to use these %'s). My question is, to more experienced investors, are these realistic expense percentages? It seems as though these are the primary expenses that are causing my negative cash flow on paper. I'd love to get your insight, and greatly appreciate the advice!