Expanding a little on what the others have already told you.

If you do not want to use a Cloud sharing option (my preference is not to had off my data to someone else), you can also take your second license and put it on a Windows machine at YOUR location.  That Windows machine can then be the primary machine that hosts the QBs Company File.  You can then add a second drive or external drive (pending any security issues) for the Backups. 

The second person can remotely access that machine and with any number of remote access software and run the software from anywhere in the world (again, pending security issues of the network you're connected to). 

So you end up with a dedicated QBs machine with Backups to a separate drive.  You have access to the shared QB file on you local network.  And the second person only needs to send keyboard, video and mouse commands across the internet, not the actual data.  (Remote access could be through the build in Windows Remote Desktop or 3rd party apps like AnyDesk, TeamView or any of the other remote desktop programs out there.)