The Ruminations blog recently posted a great list of operating expenses that Tenant's should not have to pay for. Typically when leasing office space most lease contracts will require that tenants pay for most if not all building operating expenses. While most expenses are passed through 100% to tenants they need to be aware of things that they should try to avoid paying.
Some of those operating expenses that tenants should not have to pay for are: leasing commissions, tenant improvements or other expenses landlords incur to lease space, property depreciation, capital repairs and improvement, etc. Read the full list here