Automate Order Processing for Restaurants - Cost?

Hi. I am working on a third-party service that will allow people to place orders at restaurants that provide online ordering. I would like to hire a coder to automate this process so that people can place the order on my site and then the order will be forwarded to the restaurant site. It will have to include a checkout system, order confirmation and log transactions. Initially, it needs to auto-fill in the form data on one restaurant site. The front end of my site and menu items are already done (not open to public yet). I'm just looking for an estimated cost to automate this process for one restaurant.

About how much can I expect to pay a coder to set this up?
The site is using PHP, javascript, MySQL, but all I care about is that is works in the end.

Hopefully this is enough info for a ballpark estimate. Thank you.

Edit: Soon after getting an idea of the costs I will be looking for a coder. So, if you are looking to pick up a job, have experience and can provide references, send me a PM with your contact info.