Custom Billing System

Billing System: (features needed) (can be made from existing open source PHP script and customized) - invoices created automatically when advertising campaign is assigned to business (if selected) - user can make payments via paypal, system should automatically recognize it - user can select credit card payment or cheque, which prompts for a staff member to call them for card details and to process it (no online processing for now) - invoices will become listed as red when due, and the system will email clients prior to invoices being due, and will email staff to let them know when they are overdue - monthly packages for enhanced profiles auto generate invoices, and can be paid by same methods above - staff members can add/edit/delete invoices, can add/edit/delete payments and apply them to specific invoices - user can login and view current/past invoices and current/past payments as needed - user can order enhanced profile via billing system, which depending on payment will require no interaction from staff - invoices can be downloaded In PDF format - staff can add payments, or remove them - staff panel will show totals for past 30, 60, 90 days and current year, including total collected in taxes - for staff purposes, all invoices should be added to a ‘to print’ list, or a feature to print all invoices should be included READ THIS - READ THIS - READ THIS Please specify what you will do whether it is code it from scratch or use an existing script with modifications. This will have to be integrated in a custom control panel and custom design. Please include any past references or scripts you have worked on.