Across the US, "First Time Homebuyers" are getting a great tax benefit in 2009. To be considered a First Time Buyer in the view of the IRS, you are defined as one who has not owned a home in the prior 3 years.

In Washington, DC, since 1997, "First Time Homebuyers" get a great tax benefit. To be considered a First Time Buyer in the view of the DC Tax authorities, you are defined as one who has not owned a home in the District before. If one owned a home elsewhere, one is still eligible.
IRS Tax credit is for $8,000; DC Tax credit is for $5,000.

Both phase out with higher incomes. Either credit may be used for a buyer in the District in 2009, but NOT BOTH. This is my understanding as I read the NAR guidelines, though I would strongly urge discussion with your accountant.

By the way, First Time Buyers across the US is IRS Form 5405 for $8000, while DC is IRS Form 8859.