Quadruplex Expense Estimations

[Nathan Hui]

BP People, 

I am under contract for a quad! It will be my first potential deal. Planning to house hack with FHA, very cliche.

When you calculate expenses for a quad do you set aside higher percentages of rental income for vacancy, maintenance, and cap ex? I am trying to determine realistic numbers. I do realize vacancy is relative to the market and rent rates. Also, maintenance and cap ex is highly variable. BUT in general what do you all do to accurately predict these numbers when doing analysis? OR, even better, what is your method for getting solid numbers if you don't have rules of thumb for this kind of thing?