Q. If I marry is it possible to avoid any of my fiance's debt liability?
A. Yes. First, your separate property doesn't become liable for a spouse's premarital debt simply by marrying. But community property as it comes into being does.
Secondly, to the extent you or your spouse will incur debt during marriage, prior to marriage both can agree to eliminate or restrict the creation of community property as between you. This is accomplished through a prenuptial or premarital agreement. Essentially you agree to restrict or eliminate the creation of community property in the first instance, since that will remain liable for debts incurred prior to (with some exceptions) and during the marriage, and so you can ensure that your separate property remains protected.
None of this applies to debts you jointly incur - the joint credit card, the jointly purchased car, or the jointly refinanced home. This is why creditors try to insist that both spouses sign loans.
But you can modify your behavior in order to protect yourself by not signing. It is possible to enter a post-nuptial agreement which achieves substantially the same thing, although it won't necessarily change the character of debt incurred prior to its signing but it may nonetheless eliminate future community debt by eliminating community property. Remember, as between the two of you, you cannot affect third party's rights who are not parties to your post marital agreement, and to do so may be considered a fraud upon creditors which means the agreement may be set aside and voided.
Thurman W. Arnold III
Desert Cities Divorce