My boyfriend may be moving his ex in with him...

My boyfriend and I have been dating for almost three years now. We are not living together (for many reasons, thats not what my question is about).

Last night he called me and told me that his sons mother (the child is almost 4) is losing her job within the next 60 days. She isn’t an ex in the sense that they had a long relationship…they were seeing each other only 6 weeks when she got pregnant and it basically ended soon after that (before she even found out about the pregnancy).

Anyway, he proceeded to tell me that he told her if they couldn’t pay their bills that they could both come stay with him. Now, his son obviously is a given. I have absolutely no problem with that, I would even help him with sitting when I could. However, this woman is out of the question. I understand that he wants to help her, but he already pays her over $500 a month in child support and her bad decisions in life are not his or my problem! If this ends up happening, I will have to break up with him. I have this funny feeling in my stomach though that I am overreacting. What would anyone else do? Am I wrong to expect him to let her be out on the street? (The woman has no where else to go, no friends in the area no family…)