Arathra,
Don't know if you've solved this, but I regularly get asked for something similar. What I usually tell people is to have their clients use HTTP to download the files, rather than FTP. Basically, User A uploads a file to a directory on the web server, then sends an email to User B with a direct http link to the file. That way they don't have to mess with ftp and passwords.
For one client, I made it even easier - I made a default page that scans the download directory than creates a custom branded file list with size, type, etc.