My understanding, from talking with waiters, is that they sign either annual or multi-year contracts. For waiters, assistant waiters, cabin attendants, etc., the pay is nearly zero -- with tips being the main source of income. And for a waiter... a good waiter... he or she can earn a six-figure income! But it takes time to obtain a coveted waiter position. They have no medical insurance so if they become too sick or are injured, they are returned to their homes.
Most ship's personnel work seven-day weeks and usually two or more jobs. The reason most cruise ships are flagged in foreign nations is to escape the United States' labor laws. But since there is little opportunity to spend one's money, most ship workers save large sums and often are the sole support of their families.
We were informed that with Celebrity, other than the officers, the staff and workers are contractors. Most enter into a 7 month contract, and they can renew if mutually agreed. Base wage is low for all, but the service staff can make good money (comparatively to the income levels of the countries they come from) from tips. Dinning room and specialty restaurant positions are coveted, and we were informed that a good waiter earns around $50K+ per contract. They do get room and board, but not luxury accomodations.
But keep in mind these people work long hours, we were told as many as 16 hours per day, and get 1/2 day off each week. A waiter may do duty in the dinning room at night, for two seatings, after having helped in the Buffet restaurant during the breakfast or lunch period, or both.
Many of these people have served multiple contracts over multiple years, and are cruise ship "professionals" in terms of experience and do wonderful jobs for us pax. I appreciate their efforts greatly and admire their stamina and patience.