As someone who this very day had his WAS move in with OP, let me tell you that the day he moves into his own place will hurt. When he takes his stuff out of the house, you will feel a great emptiness and loss. I'd make sure you don't let him have any pictures, sentimental stuff, etc., but do you really care about other things? Let him have them.
I'd say, though, to plan on something fun that evening to try to take your mind off it.
The LORD is near to all who call on him, to all who call on him in truth." (Psalm 145:18)
