Actually, you will only find those files in the /home/hisusername/ directory, so you won’t be able to browse to them with a browser without taking additional steps.
Fortunately, DH makes this relatively easy to do, by remapping a Sub-dir.
The wiki article linked describes how to set it up so that the /home/yourusername/yourdomain.tld/userx subdirectory can display the contents of the /home/userx directory, which should do what you want.
Be sure to note the caveats re. CGI scripts and file ownership/permissions that could come into play by doing this.
Alternately, instead of giving the other user his own ftp account and user space, you could choose to address the situation by using a file manager type CGI application to allow him to contribute content without some of these concerns. This allows him to upload content, but keeps all the files owned by your user, and makes things a lot simpler sometimes. I like, and use, ffileman for this, and it has served me well.