I have had crew for long passages and my rule
is that I pay for costs on the boat and they pay for any costs off the boat. Many people will leave it to the crew to pay for the costs of getting to and from the boat and this is perfectly OK to do - I have paid for this sometimes in order to get my pick of crew or if the time line is very short. Either way is good so long as expectations are made clear up front
As far as I am concerned they are doing me a major favor by standing watches on a set schedule for days or weeks at a time in the middle of the ocean. Competent help on passages is a really great thing and I like to treat them well. Paying for their food
and drink is a small price
for the peace of mind of having good sailors sailing my boat while I sleep. All I ask them to bring is their own foulies.