I wouldn't trust that...point out to him that even if he installs it himself that you still have access to the files, so him installing it is pointless. If he really wants to protect his software he needs to encode it with something like Ioncube.
If you really do want to go through with this though, just create a database and give him the information to it, and create a FTP account under your CPanel. Make sure you come up with a brand new password for him.
Although personally, I wouldn't give him access...