Distribution Business Automation

I have Plastic Goods (Chair, table, and other home use products) distribution business. i am currently maintaining all transaction in a paper register including Customer Information, Vendors information, Accounts, inventory, receipt and dispatch, employees information/salary details, bank transactions details, daily/Monthly/Yearly expenditures and income etc. We have three outlets within a city and for apart approx 2 Km. I need a solution that we run at main outlet and accessed from the two other outlets for the above mentioned transactions plus invoice, payment receipts and other reports generation and printing. what i have to purchase other then the software that fulfill my requirements, how i will be able to safe from data loss? How many time will be required for this project completion? any other suggestions are welcomed..