When must I pay back the credit for the home I purchased in 2009?

Generally, there is no requirement to pay back the credit for a principal residence purchased in 2009 or early 2010. The obligation to repay the credit arises only if the home ceases to be your principal residence within 36 months from the date of purchase. The full amount of the credit received becomes due on the return for the year the home ceased being your principal residence. 

If I claim the first-time homebuyer credit for a purchase in 2009 or early 2010 and stop using the property as my principal residence before the 36 month period expires after I purchase, how is the credit repaid and how long would I have to repay it?

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. Form 5405 and its instructions will be revised for tax year 2009 to include information about repayment of the credit. 

To avoid repaying the tax credit, we recommend following Dave Ramsey’s advice. Evaluate your finances before beginning the process of purchasing a home. To do this, you should calculate how much you can afford.  Next you should get pre-approved. This will allow you to get an estimate of the interest rate and payment you will have to make. If you find you can afford the estimated payment and are financially ready to purchase a home, you are prepared not to repay the tax credit.