You can use rssh or ChrootDirectory option from the new(ish) OpenSSH
$ man sshd_config
Specifies the pathname of a directory to chroot(2) to after authentication. All components of the pathname must be root-owned directories that are not
writable by any other user or group. After the chroot, sshd(8) changes the working directory to the user's home directory.
The pathname may contain the following tokens that are expanded at runtime once the connecting user has been authenticated: %% is replaced by a literal
'%', %h is replaced by the home directory of the user being authenticated, and %u is replaced by the username of that user.
The ChrootDirectory must contain the necessary files and directories to support the user's session. For an interactive session this requires at least
a shell, typically sh(1), and basic /dev nodes such as null(4), zero(4), stdin(4), stdout(4), stderr(4), arandom(4) and tty(4) devices. For file
transfer sessions using “sftp”, no additional configuration of the environment is necessary if the in-process sftp server is used, though sessions
which use logging do require /dev/log inside the chroot directory (see sftp-server(8) for details).
The default is not to chroot(2).
But unless you're paranoid (and you may have good reasons to be, I'm not judging), I'd just give the guy a regular shell account.