Individual day tickets can be sold easy via stubhub. Post them and when you get the physical tickets in late Feb from the Masters, you send them to the buyer using the shipping label provided by Stubhub. Once the tracking shows delivery, stubhub pays you. You can post them for sale as early as you wish, but when setting it up, just give a future delivery date in late March. Don't wait until you have physical tickets to sell, and don't post pictures of the physical tickets for sale. As long as you dont post pics of the tickets and arent dumb about how you list your tickets (no personal information that link them to your wife), you should be fine.
The rentals you are seeing are people with a full tournament badge trying to sell each day individually. So the badges have to be picked up in the AM and returned in the PM. Not your situation.
One word of caution - if whoever buys your pass does something to wrong the Masters staff, your wife won't ever be able to get passes again. The one risk you can't really mitigate is whether your buyer follows the rules while attending.