Couples begin working from home for many different reasons. Sometimes it's by choice, sometimes it isn't. Sometimes it's an opportunity, sometimes it's a necessity. Whatever the situation, you'll get off to a better start if you both agree that the best course of action is to work at home.
It's virtually impossible to work happily at home without the cooperation and support of your spouse, so a joint decision will most certainly work better than issuing an edict or even simply making an announcement that you've decided to work at home.