My STBXW went behind my back (after she filed) and put the house that we own together on the market. It is still on the market, and now she has it rented out (once again, behind my back) I need to move into that house since I assume the courts will decide who gets it in the end - we both have legal right to it, and she isn't living there. Why would her lawyer advise her that any of this is okay to do?
The first thing I would do, is inform the renter of the situation, and tell them, as a co-owner, that they need to write you a check for 1/2 the rent from now on.
Beyond that,you are probably within your rights to evict the renter, and move back in. Call the realtor that is selling the house, they will void the selling contract if they find you needed to also sign on the dotted line.