I would most definitely adopt a 9 year old dog.

I wouldn't be too worried about her behavior as they are tested before being put up for adoption now days.

Don't let her age bother you, depending on her diet & general health she could give you 2 to 5 years of unconditional (most probably sleepy) love... but the best thing of all is what you are giving her. A second chance. Which is a wonderful thing. One you will both feel the benefits of.

In regards to possible vet bills, wether you have a puppy or a golden oldie that is always a risk and part of the responsibility. But who cares about money when you get paid back with sloppy kisses lol.

Good Luck