What is the general cost for the NNN?

The average NNN cost varies by property type and area. To answer your question, it is standard practice for building insurance to be included in NNN and it is also highly recommended you carry business insurance as this protects you from issues that arise within your business.
It may be worthwhile to ask other businesses in the area what they are paying in NNN to help gain a better understanding of what the average NNN rate in your area is.
Please don't hesitate to let me know if you have any other questions.

It depends on the following three:
1) Property tax rate.
2) The cost to insure that specific property and which will also vary by type of property
3) the owners cost of maintenance i.e CAM.

Triple Net (NNN) charges vary by property because they generally consist of a proportionate charge back from the Landlord for Common Area Maintenance costs (CAM Charges), Landlords cost of property and fire Insurance and Real Estate taxes. They are generally paid monthly in addition to base rent or once a year after the Landlord has a chance to reconcile his costs for the past year. If his actual costs turn out to greater or less than originally anticipated he usually makes an adjustment for you as a result. The actual handling of these costs in dependent upon the terms of your lease agreement and should be clearly understood prior to making a lease commitment on your behalf.

There is no general cost for NNN. Will vary from property to property, city to city, state to state and be affected by the type of property, age, condition, location, etc. NNN - Taxes, Maintenance and Insurance. You are paying a proportionate share of the total costs of the NNN based on a % of the whole for the space you lease vs. the SF of the total property. The insurance you are paying for is general property insurance - that is part of the NNN. The other insurance you are paying for is covering your own lease space / liability, etc. and that is absolutely correct. I see NNN vary here in DFW from $2 to $8 per SF per year, divided by 12 for monthly payments and subject to being adjusted - up or down - each year after all expenses have been trued up.