A Triple Net, or NNN, lease is a contract in which the tenant is responsible for everything including; taxes, insurance, roof and common area maintenance. In this type of agreement, the landlord collects the taxes, insurance and common area maintenance fees on a monthly basis.
The key to this type of lease is that the landlord must present the building to the tenant in pristine condition or give the tenant free rent to take it as is. And at the end of the term the tenant must return the property to the landlord in pristine condition. Throughout the duration of the lease, the landlord receives an agreed upon dollar amount per month, which can be used to take care of any building related expenses, including the mortgage. Since the expenses are in addition to the base rent amount, the tenant ends up paying more per square foot gross.