I believe I am one of the lucky ones when it comes to renting with
ferrets.  My apartment manager looked through her pet rulebook, and
there was no rule for caged animals.  Even though an apartment is
supposed to have only one animal, she allowed the ferrets.  Our agreement
with her was this: If there was an inspection by upper management, the
ferrets magically disappeared.  This was easy to do since there was never
any "surprise" inspections; we always had a week's notice.  Now I have a
medical letter that allows them to stay, so we don't have to hall them
off to a pet sitter.
[Posted in FML issue 4038]