I have to almost force my wife to spend money on herself. I am very lucky to have her for 23 years.
Our communcitation is awesome. We have a rule, no one makes a purchase over $100 without the others knowledge, unless it is a bill. We even discuss purchases even smaller if it is something the both of us will potentially use.
No separate checking accounts, just a mutual understanding.
As far as a stranger coming into my home when I am not present and without my knowledge, that would be a no no too! No surprises are a key to avoid problems and as Gene pointed out, that requires good communication.