Our mortgage notes payable and line of credit, or the Line of Credit, as of March 31, 2013 and December 31, 2012 are summarized below (dollars in thousands):

Mortgage Notes Payable

As of March 31, 2013, we had 31 fixed-rate mortgage notes payable, collateralized by a total of 65 properties. Gladstone Commercial Corporation has limited recourse liabilities that could result from any one or more of the following circumstances: a borrower voluntarily filing for bankruptcy, improper conveyance of a property, fraud or material misrepresentation, misapplication or misappropriation of rents, security deposits, insurance proceeds or condemnation proceeds, or physical waste or damage to the property resulting from a borrower’s gross negligence or willful misconduct. We will also indemnify lenders against claims resulting from the presence of hazardous substances or activity involving hazardous substances in violation of environmental laws on a property. The weighted-average interest rate on the mortgage notes payable as of March 31, 2013 was 5.62%.

During the three months ended March 31, 2013, we issued one long-term mortgage, which is summarized below (dollars in thousands):

The fair value of all fixed-rate mortgage notes payable outstanding as of March 31, 2013, was $376.5 million, as compared to the carrying value stated above of $360.2 million. The fair value is calculated based on a discounted cash flow analysis, using interest rates based on management’s estimate of market interest rates on long-term debt with comparable terms. The fair value was calculated using Level 3 inputs of the hierarchy established by ASC 820, “Fair Value Measurements and Disclosures.”

Scheduled principal payments of mortgage notes payable for the remainder of 2013 and each of the five succeeding fiscal years and thereafter are as follows (in thousands):

Line of Credit

In December 2010, we procured a $50.0 million Line of Credit (with Capital One, N.A. serving as a revolving lender, a letter of credit issuer and an administrative agent and Branch Banking and Trust Company serving as an additional revolving lender and letter of credit issuer), which matures on December 28, 2013. The Line of Credit originally provided for a senior secured revolving credit facility of up to $50.0 million with a standby letter of credit sublimit of up to $20.0 million. On January 31, 2012, the Line of Credit was expanded to $75.0 million and Citizens Bank of Pennsylvania was added as a revolving lender and letter of credit issuer. Currently, 14 of our properties are pledged as collateral under our Line of Credit. The interest rate per annum applicable to the Line of Credit is equal to the London Interbank Offered Rate, or LIBOR, plus an applicable margin of up to 3.00%, depending upon our leverage. The leverage ratio used in determining the applicable margin for interest on the Line of Credit is recalculated quarterly. We are subject to an annual maintenance fee of 0.25% per year. Our ability to access this source of financing is subject to our continued ability to meet customary lending requirements, such as compliance with financial and operating covenants and our meeting certain lending limits. One such covenant requires us to limit distributions to our stockholders to 95% of our FFO, with acquisition-related costs required to be expensed under ASC 805 added back to FFO. In addition, the maximum amount we may draw under the Line of Credit is based on a percentage of the value of properties pledged as collateral to the banks, which must meet agreed upon eligibility standards.

If and when long-term mortgages are arranged for these pledged properties, the banks will release the properties from the Line of Credit and reduce the availability under the Line of Credit by the advanced amount of the released property. Conversely, as we purchase new properties meeting the eligibility standards, we may pledge these new properties to obtain additional availability under the Line of Credit. The availability under the Line of Credit is also reduced by letters of credit used in the ordinary course of business. We may use the advances under the Line of Credit for both general corporate purposes and the acquisition of new investments.

At March 31, 2013, there was $26.4 million outstanding under our Line of Credit at an interest rate of approximately 3.0% and $6.1 million outstanding under letters of credit at a weighted average interest rate of 3.0%. At March 31, 2013, the maximum additional amount we could draw was $3.9 million. We were in compliance with all covenants under the Line of Credit as of March 31, 2013. The amount outstanding on the Line of Credit as of March 31, 2013 approximates fair value, because the debt is short-term.