DH and I have totally separate finances, but we both know exactly what bills come in and what money we need to pay out, so certain bills are in my name, and I pay them, and others are in DH's name and he pays them. It works out about equal.
I don't know exactly how much DH earns, and he doesn't know how much I earn. I have never asked, and neither has he.
I work FT, DH works FT, and we both always have. 3 x DC's, all old enough to not need childcare now, but when they were, I payed the childcare and DH payed more for shopping etc, so we still payed out about the same
I know that if something happened, and DH wasn't here anymore for any reason, I could cover all bills etc, and still keep going.
Its a result of seeing my DM being financially abused by my SDF, and DH understands my need to be financially independent. He knows that I might have savings, but will be very happy when the pension comes through 
Ask your friend, is there anything in the DH's history that reflects this?
And, before anyone asks, we have been together for nearly 30 years, and it has worked all this time.