Age today is not a boundation for any kind of Aesthetic or Cosmetic Treatments
. In some cases when it is required for long term benefit to the patient we advise Ortho (Braces) treatments even at 50 years of age. The only thing is that after 18 years of age the time required to move the teeth increases with age. But that is say 6-9 months more than usual. Moreover with the invent of Lingual Ortho, a new technique where the braces are applied on the inner side of teeth, no one except you will come to know that you are wearing braces. Also there are tooth colored Braces which can be worn without getting noticed, until one is hell bent on seeing your teeth.
But I would suggest you that be doubly sure before going for Ortho treatment. I mean consult your family members and you close friends that whether you really require this treatment. I mean is it worth or in other words are your teeth severely malaligned (irregularly placed teeth)? If Yes.
Then visit a good Orthodontist
and he will explain you the treatment plan, time and cost.
It will take 2-3 years very easily. Cost will depend on the city, locality and your Orthodontist. Only I can tell is it needs a handsome amount of money.
So good Luck, God Bless and take care.