Explain the easy way to use a database on WordPress to control job with file upload/download

Status: Closed
Prize: $15
Entries Received: 10
Winner: intensivecoder

Winner

Contest Brief

I want to make a website by myself using WordPress so that customer can have an account online where he can make a registration then he will upload and download image files.
I will work on this image files and transform that image in 3 or 5 new images files and then the customer will receive a notification that the files are ready to download. Customer will login again and download the files. This will generate a job with price and customer will have to pay it before download or for some special customers we will generate an invoice later and bill all the jobs done to him.
I will pay $15.00 for someone who tells me how to do this database and the forms to do all the controls. I need a simple solution. Perhaps I can use a plugin easy to manage that database.
I use hostgator to host.