I've attached a sample plan for a cleaning service: http://www.bplans.com/cleaning_service_business_plan/executive_summary_fc.php#.UCE3T6DQgcs
While it may not be exactly the same as your business, it should look similar, and give you a good idea of where to start on the financials.
Also: have you tried browsing the web to see how much similar businesses are charging for their services? A quick Google search and I came up with a handful of office cleaning services in my area that had quote forms that can be submitted online--it is easy to see what your competition is charging. Good luck!