As soon as they start making an income, which would probably be before they even got married. I would say right away it is very important and the man and woman need to be on the same page and agree on things. You need to know if he or she has bad credit; you need to know in marriage if one person is a saver and if the other is a spender. That's a conflict right out of the gate and that is a frequent problem in marriages. Finances are one of the biggest problem causers in a marriage. I think it's a good idea to have a goal to shoot for. Not everybody is going to do it, but it is much easier to have a goal that's in writing in front of you and follow it, than it is to just say something verbally and try to follow it.
