On the unpaid trial front, I did one at a bar years ago. They interviewed me, had me try it out for an hour or two because I hadn't done it before, then offered me the job. I was applying for it because my current job only offered about sixteen hours. Went back to my current job to let them know I had gone for a job that offered me double that and that I'd be leaving - they offered me forty hours, so stuck with them and thanked the bar for the offer but my situation had improved so wouldn't be joining them. I think not paying me in that situation is perfectly fair.