Legal advice regarding mold in an apartment

[Luis Rodriguez Jr]

I need legal advice on a rental unit having mold and now my sister is stuck. She has done about 5 mold tests and all of them were oozing out. Now her , her husband and 1.5 yr old daughter are sick and the owners do not want to fix anything. Do we have a case? Can I go to her apt and fix the issues myself, just so the baby doesn't have to deal with this. What are my options?