Thanks for your responses. My addon domain also needs a separate ftp account for my users to be able to upload files, and I also need to access their data for maintenance purposes. I actually have dreamhost account but I am planing to move to another hosting which has a main shell account where I can manage everything using that account (main shell account). Having a difficulties on managing my addon domain's data on a single shell account is a show stopper for me. I am thinking about this solutions but I am not sure if it will work.
Main account shell (mainshell)
addon1.com ftp account
addon1.com >>> symlink to /home/mainshell/addon1.com
(ln -s /home/mainshell/addon1.com addon1.com)
So when addon1 ftp account login to its FTP (regular ftp port 21) account, can he open the symlink to /home/mainshell/addon1.com and can write files to it?
Hope you guys can help me here =] what about groups?