No idea about /var.
As long as you don't use the same user name then sharing /home is fine.
If you have folders with stuff you want to access from both, then one
possible solution is to make a folder at the root of /home and put them in
there, then make it readable by all. You can then symlink that folder into
appropriate home folders.
So /home would then look something like...
/home/account1
/home/account2
/home/stuff
Then in a terminal, something like 'ln -s /home/stuff/Music/*
/home/account1/Music'
