Property management question

[Priceton Braswell]

Working on deal analysis for my first deal. I see a lot of people use 8 to 10 percent of income for property management during analysis. If my tenant moves when the lease is up the property managers in my area charge a months rent plus 8 percent of monthly income to manage. One month of rent is 8 percent plus the other 8 percent is 16% of incomei for property management. Am I wrong to use that big of a number during my analysis?