People who have an ownership stake in an established business when they get married typically are advised to get a prenuptial agreement to protect their share of the business should they divorce. However, even if your business idea is still a dream, you should protect it with a prenup.
As one family law attorney notes, "Maybe you have no money, but you have a lot of potential down the road. That is something you cannot protect without a prenuptial agreement." However, as she explains, that can be "tricky" because you can't put a value on something that doesn't exist yet.