Hi Jodi,
please find below lots of useful information regarding the tax credit. The answer to your specifc question is that the property you are buying must close on or before November 30, 2009.

Please contact me directly as I would love to be of further asssistance to you.
Nick Welsh

1. What’s this new homebuyer tax incentive for 2009?
The 2008 $7500, repayable credit is increased to $8000 and the repayment feature is eliminated for 2009 purchasers. Any home that is purchased for $80,000 or more qualifies for the full $8000 amount. If the house costs less than $80,000, the credit will be 10% of the cost. Thus, if an individual purchased a home for $75,000, the credit would be $7500. It is available for the purchase of a principal residence on or after January 1, 2009 and before December 1, 2009.
2. Who is eligible?
Only first-time homebuyers are eligible. A person is considered a first-time buyer if he/she has not had any ownership interest in a home in the three years previous to the day of the 2009 purchase.
3. How does a tax credit work?
Every dollar of a tax credit reduces income taxes by a dollar. Credits are claimed on an individual’s income tax return. Thus, a qualified purchaser would figure out all the income items and exemptions and make all the calculations required to figure out his/her total tax due. Then, once the total tax owed has been computed, tax credits are applied to reduce the total tax bill. So, if before taking any credits on a tax return a person has total tax liability of $9500, an $8000 credit would wipe out all but $1500 of the tax due. ($9,500 - $8000 = $1500)
4. So what happens if the purchaser is eligible for an $8000 credit but their entire income tax liability for the year is only $6000?
This tax credit is what’s called “refundable” credit. Thus, if the eligible purchaser’s total tax liability was $6000, the IRS would send the purchaser a check for $2000. The refundable amount is the difference
FIRST-TIME HOMEBUYER TAX CREDIT
between $8000 credit amount and the amount of tax liability. ($8000 - $6000 = $2000) Most taxpayers determine their tax liability by referring to tables that the IRS prepares each year.
5. How does withholding affect my tax credit and my refund?
A few examples are provided at the end of this document. There are several steps in this calculation, but most income tax software programs are equipped to make that determination.
6. Is there an income restriction?
Yes. The income restriction is based on the tax filing status the purchaser claims when filing his/her income tax return. Individuals filing Form 1040 as Single (or Head of Household) are eligible for the credit if their income is no more than $75,000. Married couples who file a Joint return may have income of no more than $150,000.
7. How is my “income” determined?
For most individuals, income is defined and calculated in the same manner as their Adjusted Gross Income (AGI) on their 1040 income tax return. AGI includes items like wages, salaries, interest and dividends, pension and retirement earnings, rental income and a host of other elements. AGI is the final number that appears on the bottom line of the front page of an IRS Form 1040.
9. Do individuals with incomes higher than the $75,000 or $150,000 limits lose all the benefit of the credit?
Not always. The credit phases-out between $75,000 - $95,000 for singles and $150,000 - $170,000 for married filing joint. The closer a buyer comes to the maximum phase-out amount, the smaller the credit will be. The law provides a formula to gradually withdraw the credit. Thus, the credit will disappear after an individual’s income reaches $95,000 (single return) or $170,000 (joint return). For example, if a married couple had income of $165,000, their credit would be reduced by 75% as shown: Couple’s income $165,000 Income limit 150,000 Excess income $15,000 The excess income amount ($15,000 in this example) is used to form a fraction.
In this example, the disallowed portion of the credit is 75% of $8000, or $6000 ($15,000/$20,000 = 75% x $8000 = $6000) Stated another way, only 25% of the credit amount would be allowed. In this example, the allowable credit would be $2000 (25% x $8000 = $2000)
10. What’s the definition of “principal residence?”
Generally, a principal residence is the home where an individual spends most of his/her time (generally defined as more than 50%). It is also defined as “owner-occupied” housing. The term includes single-family detached housing, condos or co-ops, townhouses or any similar type of new or existing dwelling. Even some houseboats or manufactured homes count as principal residence

Jodi,

Thank you for your question.....
Attached is a helpful website that should answer this and other questions about the program in question.
http://www.federalhousingtaxcredit.com/2009/faq.php

Best wishes,
The Eckler Team

Actually the home must CLOSE before 12/01/09.

If you're referring to the 8K tax credit. A home must be purchased before 12-1-09.