^ I agree. Plus, while six months should be long enough to know whether you'd consider having someone move in with you, it still could be way to soon to do so. That is really just the beginning stages of a relationship, so it's better to be cautious and take it slowly when it comes to making a major change to your living situation. If your wife doesn't want it and "needs convincing," is there a reason you're pushing for this at this early stage? Is this something your gf wants?
The world opens up... when you do.
Oh, oh, can't you see? Love is the drug for me. ~Bryan Ferry
"Love is that condition in which another person's happiness is essential to your own." ~Robert Heinlein