You never know someone until you live with that person. Really? How about - you will find out that person's co-habitation habits and routines, BY LIVING IN THE SAME DWELLING AS THAT PERSON, however, even if you LIVE with a person for decades, you can never truly 'know' that person because people and circumstances change at the drop of a dime. TRUST NO ONE - NOT EVEN THOSE YOU'VE LIVED WITH FOR YEARS.