Back Office For Current Website

I have a wordpress website up and running. I need clients to be able to order services through the website. I need a back office where clients can login and see what they've ordered as well as their inventory with us. I install posts and lockboxes for real estate agents, we also inventory their signs and lockboxes. I need agents to be able to see their order histories, see how many posts we have in the field for them and to be able to check their current inventory with us. For example, if a client gives us 5 lockboxes and signs, and we install 3 lockboxes and signs, I need the agent to be able to see the properties the 3 lockboxes and signs are at PLUS the fact that we have 2 signs and lockboxes still in our inventory. Clients are also charged an additional fee if we keep their posts for over 6 month. I would like an auto email sent out to remind the clients. The clients need to be able to login, see current inventory and easily order a post to be removed. When the customer puts an order in, I need a shopping cart to be able to tell them what their amount owed is going to be. I will not collect fees through the website, but I want the client to know what their fee is going to be.