The first time homebuyer tax credit provides for the reduction of the income tax liability of the homebuyer on a dollar for dollar basis. The homebuyer must itemize all deductions, including income and exemptions for the tax year, among other things, to determine their tax liability. If you qualify for the $7,500 tax credit and your total tax liability for the tax year is $7,500, it becomes a wash and you owe nothing for that year. If the equivalent of $7,500 was deducted from your paycheck during the course of the year by your employer, then you should receive a tax refund of $7,500.
Please note that First time homebuyer tax credit is more like an interest-free loan that must be repaid over a period of 15 years.