– what kind of syncing would you expect?

I would like the databases to be able to update each other, and to move the associated files as well. That way I have a mirror copy on each machine.

– how do you expect it to work?

Here is the gotcha. Most examples I have worked on in the past do it through a client server model. I think that could be an option for the business side, but I am not sure if it would be the best method for the other versions. The old one I used you could work offline, and then it would sync up with the main database. The only concern would be if multiple people had the same file, but you can have an option for check out.
The key is the database, and the files would have to be kept in sync for it to work correctly. You could either do a "server" side database with an offline option, or two seperate databases that try to sync each other when connected.
Are you using the access engine for the backend DB?

Already bought the business version. 😉