Another person living within the property cohabiting

At present, my x is living in a 4/5 bedroom house paid for by the state, and that is living off benefits. The problem is that her solicitor has wanted within the Trust Declaration to be added a clause say 6 months.
This trial to see if their client can cohabit with another person staying for that period I would have no way of checking so after 6 months he leaves and she gets another to stay this could go on and on.
I have not agreed if need be go back to court children age 17/13 like I said x has no outgoings picks up CMS the state pays the interest only on the FH doesn't work and the other trimmings from the state DWP X is playing the system if the house is sold would have enough collateral to rent or even put down a down payment on a property that the children would be settled for the next 8 to 10 years settled. X also is responsible for maintaining and paying all the bills and insurance. X is on legal Aid has no funds etcThe courts would not allow this to be written in or?