If memory serves me right if you can't legally own one then the wife can't as long as the 2 of you are living under the same roof. I'm quite sure that if I'm wrong I'll be corrected
Here's your correction...
Prohibited persons can live under the same roof, as long as they do not have access to the firearms. That means the guns have to be locked up, and the prohibited person cannot know the safe combination, or have access to the keys.
If the keys are on the key ring with her car keys, and you drive her car, you have "access" and are in violation. If the keys hang up where you can get them, you are in violation. Get the picture. If the prohibited person would have to physcially break open the safe to get the guns, your are ok.
If you are not a prohibited person, wifey can buy you a gun and give it to you as a gift. She can buy it for herself, and loan it to you sometime. But she can't legally buy a gun "for you".