As I have mentioned in other blogs, it all depends on how much experience you have and if the job will benefit your portfolio, resume and reel. As a new model I got tearsheets without pay, but it was worth it because it gave me a great experience, working with professionals, and it lead to working with modeling agencies. I used the tearsheets to make a compcard and kept hustling them and mailing them out and got an agency working with me from it. And I got more confidence as well.
It felt good to know I could get my own tearsheets too.
Also if you think the director and crew are quality you should still do a check up on them. You want to make sure you do a background check on the crew, production company, casting director and director and photographers you work with for that go to Google!
If the work, credits, resume don't seem quality...don't sweat it, move on, there is more work out there.