It seems to me that no manufacturing business can really survive without a credit line of some kind. It’s a simple fact that if you are producing a product, you must pay for the materials to make that product long before you will be paid for the final product unless you can manage collecting payment in full when you receive the purchase order from your customer.
Most of your customers will ask for and deserve payment terms of some kind. These payment terms usually state something like “Net 30 Days”. This means that the customer promises to pay for the goods invoiced in 30 days from the date of the invoice.