I normally sail alone but have taken on crew for both an Atlantic transit and traveling around the Caribbean. My particular rule is crew contributes to food, pays for their own customs fees (rare), alcohol, smokes and entertainment. This usually ends up being about $10 to $20 per day (some people like steak, some mac and cheese!) I think this is fair. The crew do not add to my financial burden and they get the enjoyment of the experience. I am not talking about taking friends or acquaintances out for a day sail or a weekend, but rather crew that stays on the boat for several months. These are people who almost exclusively have asked to go sailing for their personal enjoyment. I feel no obligation to pay their costs.
A touchy issue is when crew break things. Cruising boats have things break and I pay the bill. But I have had people drop winch handles overboard, throw dishes into the sea when emptying grey water, and drop expensive electronic remotes overboard. The polite ones pay, the others seem to think I am made of money.
A second issue is what belongs to me and what belongs to the boat. I have had guests assume they can use my computer, my camera, etc. because they are on the boat. I don't agree.
A third issue is cleanliness. I try to keep the boat very clean. Traveling in the tropics it is difficult to keep bugs off the boat. I have had to ask people to leave who do not understand the necessity of keeping the food and kitchen area immaculate.
I have added links to two documents that I use to "interview" potential crew and explain their duties. You are welcome to comment on them and/or use them for your own purposes.
Potential Crew Questionare: https://docs.google.com/file/d/0B2Dn...it?usp=sharing
Standing Orders: https://docs.google.com/file/d/0B2Dn...it?usp=sharing
A final note: There are many people in the sailing community (like any other community) that are trying to make money on their "dream." There are people willing to contribute to sail on a tall ship etc. I have no problem with that. I do have a problem with people running a commercial venture who try and pretend it is something else.