Maybe the person who is marrying for money is really married to money already. While I can understand how one could fall in love with money, I don't think it is a good strategy for happiness and to use the old Kantian language, you would certainly be using your spouse -to-be purely as a means to an end. Now, if you confided to that person that you would not want to marry them were it not for their$, then perhaps that would be something different. But you certainly couldn't honestly promise to love him or her. In most cases, there would be a lot wrong in marrying for money.