Correct. Only one user at a time and you just send the file between the computers. I use a sync program between my Notebook and my Desktop computer and basically do the same thing every time I travel. I move all my User Data over to the Notebook for my trip and then move it back to the Desktop when I return.
You would stop working on QBs in the Office and copy the QBs Data Folder (not the whole program) up to Dropbox (MS OneDrive or whatever) and then the Remote User would download that info to their computer. They'd do the work and then upload back to the Cloud.
NOTE: Above I had said Company File, which would work. But I'd actually suggest you move the folder that has the Company Data in it. So if you have any logos for Invoices, etc. they will be on both computers and updated if they change.
Gotchas are if someone forgets and does work while the other user "owns" the file. But there are a couple of ways to get around that. When you copy the folder up to the Cloud you can put an X at the end of the folder which would keep QBs from opening it, but it would still be there if something happened to the data in the upload. Next time you go to update the data, delete the last X folder and rename the current folder with an X after it and the cycle continues.
Also, if you're using the Cloud for transfers, you can also set up a separate Folder for Backups and BOTH computers can backup to this Folder. With time/date stamp both users can make a Backup to this folder with no issues. (And there is the last folder on the other machine as another backup.) And yes, if you're thinking you could do a Backup and the other machine could do a Recovery, you could. Down side to this is the compression and decompression of the data. It's just not worth the chance of corruption.
Also, let's clarify that you are NOT in Multi User mode. Your are operating in Single User mode since you're just running one installation at a time. And yes, if you really needed to look something up, you could also remove the X on the end of the data folder and open QBs and it will work just fine (again,you're just in Single User mode). But you just have to remember NOT to do any additions, Bank Feeds, etc. while the Company File is "owned" by the other computer.
If you don't need to do a lot of work, generate Invoices all the time, etc. in both locations, this will work. And you can always try it and see if it works.
And... Always remember to run Windows and QB updates on all the machines, preferably the same day.