there are some hostels in farolones, I'm pretty sure that's the cheapest place to stay and ski the areas outside santiago (valle nevado, la parva, and el colorado) you can buy a ticket to each place individually or one that gets you all three, but skiing from mountain to mountain is not the easiest. I've heard about a hostel in santiago that runs a shuttle up to the hill everday if they have enough ppl. but i don't know that much about it.
as mentioned before check out TGR forums and they might have a little more info. suerte,