I have a great aunt and uncle (they're elderly now) who have been living in separate houses for decades but they're still married. She still goes to his house and cooks, cleans and does his laundry. Not sure what on earth she gets out of the deal but hey, whatever works.
I know a mom who has been wanting to leave her husband for at least 10 years. She works, he's an "unemployed" plumber. Really? Hasn't been able to find any plumbing work in 10 years? Anyway...he has a bedroom in the basement and uses some shared spaces (kitchen, bathroom) but she and her daughter have the rest of the house.
Honestly, I think if I were your friend I'd bite the bullet and leave him and go on welfare or whatever until I could get back on my feet (I would also stop dating, having babies and marrying losers). There are daycare and housing subsidies for the truly poor. It would suck, but she needs to learn how to support herself and her child and stop living off of bad men.