Need you ladies!!!

Ladies, I really need your advice!! My husband and I are getting into kind of a situation here soon. My mother is unable to walk or stand much due to an infection in her body, but mostly her legs. She is unable to work. I plan on trying to have her apply for disability, but idk if she will. She used to be a drug addict, and to be honest, idk if she still is or not. I really hope not. Anyway, my husband and I recently bought a house and have a spare room. Since she can’t work, she also can’t pay rent. She will be coming to live with us or she will end up homeless. We have to try and find a way to store all of her belongings. But what I really need help with is hopefully you ladies can think of some good guidelines or rules that need to be put in place to help protect my husband and I and our relationship. I know it’s hard to do without knowing the relationships, but any ideas are appreciated. Thank you.