A Triple Net Commercial Lease Agreement (or NNN Lease) is a lease agreement between a tenant and a landlord where the tenant is responsible for all taxes, insurance and maintenance costs associated with the property. This type of lease agreement is commonly used in retail and office space leases. The tenant must pay a base rent plus the taxes, insurance and maintenance costs. The landlord is responsible for the upkeep of the building, but the tenant is responsible for all other costs. There are two main types of Triple Net Commercial Lease Agreements: Gross Lease and Modified Gross Lease. In a Gross Lease, the tenant pays a flat rate for the space, and the landlord pays all expenses associated with the property. In a Modified Gross Lease, the tenant pays a base rent plus a portion of the operating expenses.