Build a Website for Online invoicing software for small businesses in INDIA

We need a website for handling dispatch labels, invoices and receipts of small online businesses. We do not need complete accounting software. In this website, we want to handle the sales of a business by entering each sale and then it can create the dispatch label to dispatch the item to customer and it should print the dispatch label. Also it should create the invoice for the sold item to send to customer along with the packet. If the item is received by the customer and money is paid, then this allows to make it as a receipt. The returned items should be cancelled and the invoices too. Other invoices will be outstanding, which are neither received nor returned. It should handle many businesses in it. I mean we need to define the business and then it can do all functioning for them. Any business should be able to see their invices only, not others. Also there should be accesses at every level and fully secured and managed. Please come up with a small document on how you will proceed on it and what all you can do in it . The winner will get many more projects also in future.