B2B Site

Hi Guys, It looks pretty likely that I will be working on a site with a catalogue that allows suppliers and buyers to log in and add products. The site must be secure in how it handles people logging in. If the site is put over a secure connection then does that mean that it is secure as this encrytps data between the server and the browser. Then when the users want to download orders they can log in and download them over a secure connection. I will not be sending them the order by email as this is not secure. Does this sound genereally secure enough? Or are there a great deal more security concerns that I should be thinking about. Thanks, Abe