As far as it being a sin, I don't know and don't think so, but I do believe it is the man's responsibility to provide for his family.
I don't think there is anything wrong with a wife wanting to work, or holding a job. I don't think it should be an expectation. I do think it is extremely important for parents to be involved in the raising of their kids. One of the parents should be a full-time parent. "traditionally" the man is the bread winner, but depending on circumstances things can be switched around. Sometimes, it might make sense to approach a situation differently.
That being said, unless such a situation comes up, a man should expect to pay for absolutely everything. (not to say that always needs to be the case, but that should be the expectation. To the men that don't agree with this: stop being wimps.)
For myself, I have made choices with this in mind. Someday, Lord willing, I hope to get married and raise a family. Until then, I have picked a career path that will allow me to support a family. I do my work heartily as unto the Lord, and try to progress in my career.
It could very well be the case that I meet a women who makes more than me, and it might make more sense at some point in the future for me to stay home with kids and her to continue working, but my mindset is that I'm the one responsible for that.
Side note, on women making more/equivalent money to men. This really depends on the company they are working for, and the field of work. I can say that when working at Intel, the women there were treated with complete respect, and they also were getting the same amount of pay as the men. This hasn't always been the case at other companies that I've worked at, sometimes due to discrimination, and others due to lesser or lower quality work, or less experience.