An after-acquired property clause in a prepetition security agreement does not create a security interest in property acquired by the debtor of the estate after the filing of the Bankruptcy petition. An exemption provides that if the security interest includes collateral the debtor acquired prior to bankruptcy and also the proceeds, rents, profits, products or offspring of the collateral, then the security interest is valid as to any such proceeds that the estate obtains post-petition. Often the granting by the debtor of post-petitions liens on assets to the pre-petition lender is a condition to the use of cash collateral.