How do I automatically get bills of new Invoice i create.

How do I get automatically get bills after I make a invoice.
Invoice being selling price and bill being the price i bought the product for.

Can you please elaborate on what you're exactly trying to achieve?

when i get make an invoice for a product can I automatically get a purchase bill for the same product at the bought price for the item.

Yes this is a great idea. One would expect the automation app to handle that but it doesn't.

When a invoice is generated (for example it syncs your ecommerce store) a bill will also get generated, since we already know the cost of the items, and we know we had to have them in order to sell them.