Your fiance is incorrect if you plan to reside in Minnesota, if my understanding of Minnesota family law is correct (attorneys licensed to practice in Minnesota are welcomed to comment below). Minnesota is a common-law state when it comes to family law, unlike Wisconsin, California, Texas and the other community property states. If you plan to reside in one of the community property states then your fiance's interpretation of the law is correct.
Under Minnesota 518.58 Division of Marital Property, dividing property at divorce, "The court shall base its findings on all relevant factors including the length of the marriage, any prior marriage of a party, the age, health, station, occupation, amount and sources of income, vocational skills, employability, estate, liabilities, needs, opportunity for future acquisition of capital assets, and income of each party. The court shall also consider the contribution of each in the acquisition, preservation, depreciation or appreciation in the amount or value of the marital property..."
This language is contrary to community property doctrine and is consistent with common-law family law.
It is understandable your fiance would be reluctant to marry someone with debt after being married to a partner who racked-up $250,000 in gambling debt and caused a foreclosure. If you plan to reside in Minnesota then your fiance has state law on his side. However, to protect both of your interests if you move to a community property state unexpectedly, then consider a pre-nuptial agreement that spells out your rights and obligations regarding the debts you incur before and during the marriage. Consult with an attorney who has experience in family law to draft such an agreement.
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