Bad living conditions, how to handle the rent

[Michael Stuck]

I am asking the following question for a family member and want to give them advice:

They are living in a poor condition older home and the AC has been broken for months and they also have water leaking in the basement to the point that they have coolers collecting the water to prevent it from soaking everything.   The catch is they are also behind in rent and have poor credit.  What can they do here?  It has been 100+ the past few weeks in Missouri.  They have been renting this place for the past 15 years and the area is expensive so Im not sure they can go somewhere else very easily.  The place needs thousands in repairs to make it what I would deem "livable" again.