Well, there's the whole Mormon polygamy thing.. .. or if he's called to go door-to-door trying to assault people with Mormonism and drags you along... Other than that, who knows?

Apart from typical mixed-faith marriage issues, there isn't much. With a husband who is a member of the Church of Jesus Christ of Latter-day Saints, your family will have home teachers. They are basically members who try to visit your home about monthly. They usually share a spiritual message and try to act in the capacity of friends. They try to make themselves aware of any problems the families they visit may be facing so that they, one of the priesthood auxiliary groups, or the church, can provide assistance. If for some reason, you and your husband find that the home teachers are an unbearable nuisance, it is possible get get one's self onto a "do not contact" list. The only things that I can think of that would be something of a nuisance to a non-member might be the spiritual message and their desire to help you and your children to be baptized. For yourself, of course, it is a simple matter to let your home teachers know exactly where you stand in regards to that issue. For your children, when you have them, this is a very typical mixed-faith issue that you and your fiance should have worked out before you get married. What church will they join? Whatever arrangement you come to agree on, there should be an agreement and it should be clearly communicated from the outset. If your fiance is endowed, he will most probably wear garments. The biggest issue though, is the children. Save them a lot of grief and do them what justice you can, by being consistent and agreed about how and what to teach them.

If your Fiance is AN ACTIVE MORMON you should already know what kind of problems it will lead to, haven't you spent a considerable amount of time with this person? Has this NEVER been talked about before? Mixed faith marriages are common and can work, you just need to talk about it before hand to ensure you are on the same page, otherwise you may have issues later on that neither of you are willing you budge on. Where will your children be baptised for example?