Hi and welcome to Just Answer! 1. How do you define 'legal residence' or 'permanent residence'? The definition depends on the purpose. For federal tax purposes - if you have two homes and live in both of them, your main home is ordinarily the one you live in most of the time. In addition to the amount of time you live in each home, other factors are relevant in determining which home is your main home. Those factors include the following.
Your place of employment.
The location of your family members' main home.
Your mailing address for bills and correspondence.
The address listed on your:
Federal and state tax returns,
Car registration, and
Voter registration card.
The location of the banks you use.
The location of recreational clubs and religious organizations of which you are a member.
2. Though we are not listed on each others' mortgage, does this mean we both own a second home now (in SC)? No it doesn't. A legal owner of a real property generally is the person listed on title.3. Should we file jointly or separately next year? If you will be married on the last day of the year - you may choose either file a joint tax return or separate tax returns. In most situation - filing jointly is more beneficial from tax refund prospective.4. Will I have to pay back the new home owner's tax credit ($8,000) I received last year?In some circumstances - yes. If, within 36 months of the date of purchase, the property is no longer used as your principal residence, you are required to repay the credit. Repayment of the full amount of the credit is due at the time the income tax return for the year the home ceased to be your principal residence is due. The full amount of the credit is reflected as additional tax on that year's tax return. See here some repayment triggers - http://www.irs.gov/individuals/article/0,,id=233589,00.html