Looking back the past couple of years, I have been between 25-30% expense ratio. Off years were for start up, and very large computer or office equipment purchases.
My expenses are generally for:
2 REALTOR/MLS boards.
Subscription to private sales data service. (Kinda expensive, but worth it.)
Advertising & other social things like sponsoring a Realtor Board lunch, fund-raiser golf tournament, etc.
CE classed for me and my father (retired, but still dips his toes in the water)
Phone, Fax service, cell phone, and DSL internet.
Occasional paper purchases (

99.9% is EDI :wink: )
Laser printer and ink jet printer supplies. Not too expensive if you shop around on the net.
At least one hardware purchase/upgrade every year. I never know what it is, but it seems that something breaks or gives out every year.
Software purchases/upgrades.
Oh, and business development......... country club golf membership.
I think those are the major things, I'm sure I'm forgetting something, but it must not be too big of an expense. As for my office, I work at home. So I don't really have any expenses there, I take the tax deduction.