USDA Rural Development Loan Program Requirements - http://usdalenders.org
There are two primary types of USDA loans for rural home financing. They are:
Rural Development Guaranteed Loan
Rural Development Direct Loan
The Direct Loan is the USDA's loan program where the underwriting and financing is handled by the agency itself. The USDA provides a guarantee to protect the lender in case of default in the future. It is currently the only available 100% Financing available for purchasing rural homes. Basically it's a zero down payment loan.
There is also no monthly MI/MIP and a just a 620 Minimum Credit Score is all that's needed in most cases.