Oh you mean a "person" PHP coder, sorry....
That would take a few days to make the shopping cart and secure payment pages. Are you expecting to buy an SSL Certificate?
Have you got a website now? Does it use cPanel?
The login script would be easy enough to do, and if you have cPanel, with Fantastico built-in, there are about 3 shopping carts ready to be installed at the click of a button.