Need info on ADA laws regarding housing (see inside)?

My granddaughter (who is in high school) has just started using a wheelchair, and they live in a 3rd floor walk up apartment. My daughter is concerned that if they try to push the issue and break the lease so they can move into a ground floor apartment, the apartment managers will charge them the $500 “lease break fee”. My daughter tells me they do have people who run the office and help run the day-to-day, but that the management is off site and generally is pretty grasping and insensitive.

I know I could wade through all the legal mumbo-jumbo in the ADA, or maybe I could just ask you guys!

I would really like to get a link to the law (if there is one) that would address this issue so if they need to, my daughter could print it off, hand it to the apartment management, and thus avoid a lot of hassle.