lodging
There are several basic lodgings in the park called "Refugios". If you plan on staying in those, make reservations well in advance. The cost for a dorm bed is about US$40.
camping
There are several campsites. Camping near a refugio costs Ch$3.500 or Ch$4000 - 5000 the other campsites are free. Away from a refugio you may find the pitches very small and on steep ground. All campsites have at least basic toilet facilities bring your own toilet paper. Despite warnings there seemed no need to book camping spots even in peak season.