A double net lease (NN) is a lease in which the tenant pays property taxes and insurance, while the landlord usually keeps roof, structure, and some maintenance.
Under a double net lease the tenant handles property taxes and insurance while the landlord remains responsible for the roof and structure, and sometimes parking lot maintenance. This leaves the landlord with some exposure to repair and replacement costs, so investors should plan a reserve and examine the building's condition. A NN property may be priced differently from a NNN property for that reason. Read the lease to see exactly which items stay with the landlord.