If you used eg Centos (free version of RHEL) as your server, & you only need (secure) FTP functionality, then you could use sftp, part of the ssh SW suite. For external access I'd definitely use sftp. You can use the Filezilla client for access.
You'll have to fwd port 22 through your router/firewall.
You can use the RHEL Admin guide to manage it: http://www.linuxtopia.org/online_boo...ion/index.html