With an unlimited web hosting service like Hostony or Hostgator, you are allowed to setup unlimited FTP accounts. That means you can setup FTP accounts for each domain you have. Besides the login name, you also need to determine the quota of each account.

Notice that there are three types of FTP accounts provided by Hostgator: Main Account, Sub Account and Anonymous. While Your main account gives ftp access to all files in your web hosting account, sub accounts provide ftp access to the user’s specific directory and all sub directories within that directory. In the mean time, Anonymous ftp users allow anonymous ftp connections to your site.