There are two types of bullet loan: Invoice Financing and Purchase Order Financing.
Invoice Financing enables you to fulfill the next order while waiting for the payment of your other customers. Once your customer paid the invoice that you issued to them, you need to repay the loan amount that you borrowed with interest.
Purchase Order Financing enables you to fulfill a purchase order request from your buyer. Once you receive the payment for that order, you repay the financing amount that you borrowed with interest.