On working for free…
I know this is a really thorny issue, but here are my thoughts.
Sometimes payment is not monetary. Occasionally, even more than occasionally, I do a gig for the experience, to learn the rôle, to sing in front of someone who will be there, to add something to my cv, to repay a favour, to help a charity, in short, I speculate to accumulate. All of these outcomes can help me to get more work in the future. In an ideal world we would never be asked to sing for free, as a favour, pro bono, but this world is less than ideal so I choose to see my fee always arriving into my life but not always into my bank account.
On the other hand, if someone has money to spare but is just being tight or unrealistic, say no. To sing for people who can afford to pay you, for instance if they are paying someone else but not you, undermines your status as a professional.
This is so tough for us all, but we have to evaluate on a project by project basis. Some things I might say yes to, others would say no to and vice versa. You must be your own police on this issue, striking a balance between missing out on opportunities and becoming classified as an amateur.