Betty has recently been diagnosed with bipolar disorder. Before she was diagnosed, she missed work many times due to severe mood swings and depression. Because of her poor performance at work, Betty was fired from her job and could not pay rent. Now she has an eviction on her record from that time.
Betty is looking for a new home. She applied at an apartment that has a policy against renting to anyone with an eviction record. Betty could ask for a "reasonable accommodation." She could ask the landlord to adjust the rules in her case because her eviction happened because of her mental illness.
But Betty has to give the landlord some kind of guarantee that she can follow the lease and pay her rent in the future. This could be things like proof that she is controlling her bipolar disorder with medication. Or a letter from her boss stating that she is reliable and has not missed work. She could also offer to pay an extra damage deposit.