Payments under section 3801 of this title for commercial products and commercial services may be made under such terms and conditions as the head of the agency determines are appropriate or customary in the commercial marketplace and are in the best interests of the United States.

The head of the agency shall obtain adequate security for such payments. If the security is in the form of a lien in favor of the United States, such lien is paramount to all other liens and is effective immediately upon the first payment, without filing, notice, or other action by the United States.

Advance payments made under section 3801 of this title for commercial products and commercial services may include payments, in a total amount of not more than 15 percent of the contract price, in advance of any performance of work under the contract.

The conditions of sections 3803 and 3804 of this title need not be applied if they would be inconsistent, as determined by the head of the agency, with commercial terms and conditions pursuant to this section.