Flash / Flex Custom Image Application

I have a custom flex application that allows users create custom images of specified sizes by adding/modifying a preset set of layers they can choose from. The images are then saved off to the server and included in our custom shopping cart system. We print the images on a material and mail them to the customer. This is much like a custom sticker generator. The database is in mysql and the site is in php. Selected developer will need these skills as well as the flex application must interact with the xml/php/mysql modules in order to complete the order processing. This is an existing application but the previous developer is no longer available. I also am not able to acquire a current version of the source code. I need the following: 1) Existing version of the source code compiled and placed on my server so that I can identify the gaps between current live version and version of source 2) Modifications of source code to meet my requirements (I will not know these requirements until I have #1) 3) This is a growing application that will require support, modifications, and feature enhancements over time. Those are obviously billable projects, however I need to know that the selected developer will a) provide me with all source files after all changes and b) be available for continued support.