I don't really know anything about this. I don't have experience with a situation such as you describe. But I noticed you had yet to receive replies to this post. So I thought I would write one.

There appear to me to be two issues here. One is legal / financial and for that I would think an attorney would be your best source of counsel. The other is interpersonal... can the two of you continue living together cordially while no longer conducting yourselves as though you were still married or in a committed relationship. And, in order to sort through that, I would think the two of you spending some time in couples counseling might be the best way to proceed.

The other alternative is to simply go ahead, do it, & see what happens. (I'm assuming your spouse / partner is on board with this idea of course. If not then I don't see how an arrangement such as this would be possible.) And, depending on the temperaments of you & your spouse / partner, that may work or it may not in which case the two of you will have to pick up the pieces & come up with a Plan B. My personal prejudice would be to go into something such as this with as much pre-planning in place as possible. But that's just me. How you proceed probably has a lot to do with your, & your spouse's / partner's, tolerance for uncertainty & ability to make good decisions on the fly so to speak. Some people can probably pull that off. It wouldn't work for me.