Unless this is black and white in the contract then do it, otherwise I would be very wary. Don't simply believe what you have been told by flying schools or interview prep companies.
I don't advocate cadetships myself, but I know of someone who did the Jetstar cadetship and the pay situation was as Damien1989 described, pretty ordinary pay for the first 18 months or so (but still better than GA), then onto normal FO wage, regardless of holding an ATPL or not (but of course they would have their ATPL subjects). Regardless, I see cadetships in the future as just a big a stream if not bigger for airline entry as direct entry from GA and the military.