To tootall re: good sync
I use a program called Good Sync Pro for Mac. It allows me to sync any folder or file, including keychain to any other computer, Mac or Win across any paired or network or FTP connection.
This is extremely useful for syncing not only my User Folder between 3 MACs but my "joint folders". I can keep a folder for home maintenance, taxes, contracts, banking, etc that both myself and my spouse need to be able to access and modify on my Macs or his Windows.
Good Sync not only keeps our shared folders synced, it also does an auto backup and user controlled archive. Under Goid Sync, the back up device is not required to be connected directly to the computer.
For others dealing with file syncs between different user accounts it is a complement to the other storage sync solutions mentioned.