How to correctly provide access to the site to a freelancer on a VPS?

Question

Access rights

Hello.
How to securely grant access to the site to a freelancer so that he has access only to a specific directory (var/www/mysite.ru)?
I go to the server via SFTP with a key file. It costs Ubuntu 16.04. Without control panel. There is no FTP server.

Answer 1

make a separate user with a cheat on this folder

Answer 2

install proftpd. It's simple. Then add the user using the command
uid and gid are usually identifiers of the www group and the user www, on behalf of which the web server is running