24 CFR §200.63

1. (a)Deposits. Where the Commissioner requires the mortgagor to make a deposit of cash or securities, such deposit shall be with the mortgagee or a depository acceptable to the mortgagee. The deposit shall be held by the mortgagee in a special account or by the depository under an appropriate agreement approved by the Commissioner.
2. (b)Letter of credit. Where the use of a letter of credit is acceptable to the Commissioner in lieu of a deposit of cash or securities, the letter of credit shall be issued to the mortgagee by a banking institution and shall be unconditional and irrevocable:
   1. (1)The mortgagee of record may not be the issuer of any letter of credit without the prior written consent of the Commissioner.
   2. (2)The mortgagee shall be responsible to the Commissioner for collection under the letter of credit. In the event a demand for payment thereunder is not immediately met, the mortgagee shall immediately provide a cash deposit equivalent to the undrawn balance of the letter of credit.