Hi 4, honestly, I can see his point in your not telling him before you sent the text. It would have been great if it had been from the both of you. Very, very often difficult children try to divide and conquer. Don't give her a reason to even think that is going to work as a strategy. You and your husband must be on the same page, or this doesn't have a prayer of working for even a week.
Second, I would have a timeline for this new arrangement. Three months? Six months? Whatever makes sense for you two.
Is she in college? If so, a full class load and a part-time job.
If not, a full time job and paying something in rent to you two---even if it's $25 a week.
And, I would get clear with him about what the agreed-upon process will be to stop the arrangement, and under what conditions, from the very beginning.
difficult children muddy the water very very well, and when it's right in front of you both, and you're furious and he's feeling sorry for her, people tend to lose their common sense.
Having things spelled out ahead of time could be very helpful---even writing down what you two agree on, so you don't forget.
Good luck! Bless you.
