Build a Website

I need a wordpress website developed. I will be purchasing a theme on ThemeForest or TemplateMonster. Not only will the theme need to be customized to our needs, I need this backend customization: Customizations: The website is a B2B (Business-to-business) type website only catering to other businesses. It needs to allow businesses to register and sign up with our services. Once approved, in the backend when the clients login, they will each have access to 1 dedicated page to them which will have a coupon generator. The coupon generator will need to generate coupons based on 5-6 different inputs (different rules for different coupons), and also generate reports and monthly invoices and purchase orders should be automated between the client and the company. The invoices/purchase orders should be generated automatically in pdf format and stored on the website (archived). The backend should support reporting on any variable like client(s), time frame, type of coupon, etc for the company. This website needs to be secure, have a proper front end, and the backend for each client should be secure and isolated for each customer to have their own coupon generator page. The website admin, the company itself, should oversee all the clients, have access to the coupons, be able to approve/disapprove coupons (this should be rule based depending on what coupon is offered by the company).