Expos are kind of a crap shoot and even if you purchase a snake from a quality vendor there's no guarantee that the stock on the table next to his isn't sick or full of mites. So I would definitely plan on a minimum 90-day quarantine.
If you still want to buy a female breeder get a virgin about 1200 grams or so and use her quarantine period to get her up to size. She will be a little less expensive and you can start pairing her early next year, they breed year-round.