My webhost has a wiki page about how to give a subuser access to a particular directory, but I tried it, it doesn't work, and they don't provide any support for that kind of setup.
Here's what I did:
(1) Created the main user ("main") and the directory ("thedirectory") I want both to be able to edit.
(2) Created the subuser ("subuser").
(3) Created a Unix group ("thegroup") and put both users in it.
(4) Assign the group to the directory with this: chgrp -R thegroup thedirectory
(5) Set the permissions for the directory with this: chmod -R g+rwxs thedirectory
(6) Log in as the subuser and create a symbolic link with this: ln -s /home/main/example.com/thedirectory /home/subuser/
The symbolic link gets created just fine, but when I try to cd to it I get the error "Permission denied". I double-checked thedirectory and its group is indeed "thegroup", and the permissions for group are read/write/execute.
So I'm stumped. Any ideas?