– If you buy a house under both of your names and you file as married separately, both of you would be eligible for $4000 credit each, and both of you would be subject to $75,000 income caps.
– If you buy a house under your wife’s name and you file as married separately, your wife would be eligible for $4000 credit, subject to her income cap, and you wouldn’t be eligible for anything. That makes you worse off than in the first scenario.
– If you file a joint return, it does not matter whose name is on the deed.
I am not a CPA or a financial advisor, be sure to double check with a licensed professional.