I own a house, and I live in there with my father and my brother. I recently was notified that my brother is getting married with his ex girlfriend, since they are back together. My concern are these: 1) she broke up with him a few years ago when our mother died, and he became unemployed and no longer could help her $financially$, also, 2) she spent the last years rejecting him, and then suddenly he got a job, is doing better financially and now she's "in love with him" and (3) They ask me if they can stay with us in the house in order to help me and my dad with the monthly expenses, since if they get a separate home, he will not be able to help as at all. Their condition is that I let them make sort of like an improvement to the balcony which is now open, but they want to close it and turn it into a reception or room in order for her to use it as an an office.
I don't want to judge her, but given the mentioned facts, what may be the reasons she wants to get into my house? Shall I agree to that? How could that decision affect my stability or my home if they invest $$$ on improvements to my home?
Please give advice