How do I know how much I can claim for the home buyer's credit?

There are no federal tax credits for buying a home.    There used to be, a long time ago, but those have since expired.   There are deductions available to you as a homeowner that can reduce your tax bill.   Here are some other things to keep in mind:

• If you itemize your deductions, you may be able to deduct property taxes, mortgage interest, loan interest, points, and home improvements required for medical care.
• Save receipts and records for all improvements you make to your home. While you can’t deduct home improvement expenses now, their cost can reduce your gain—along with any capital-gains tax—if you sell in the future.
• If you sold your home to buy this one, you won’t pay taxes on the first $250,000 (also known as a gain) as long as you owned the home and it was your main home for at least two years within the five years leading up to the sale. If you file jointly, you won't pay taxes on the first $500,000. 

Please see - - I bought a house, what can I deduct?

If you take an early withdrawal from your IRA…..

If you qualify as a "first time home buyer", the first $10,000 can be exempt from the 10% penalty for early withdrawal.  And that is for each spouse's withdrawal.