A first-time homebuyer is a buyer who has not owned a principal residence during the three-year period prior to the purchase. For married taxpayers, the home ownership history of both the taxpayer and spouse are considered. For example, if you have not owned a home in the past three years, but your spouse has owned a principal residence, neither you nor your spouse qualifies for the First-Time Homebuyer Credit. Ownership of a vacation home or rental property not used as a principal residence does not disqualify a buyer as a first-time homebuyer.
Starting in 2011, the First-Time Homebuyer Credit is only available to members of the uniformed services or foreign service, or an employee of the intelligence community, and on qualified official extended duty outside of the United States for at least 90 days between January 1, 2009 and April 30, 2010.