I help out with recruitment occasionally and as a matter of course any CV with a TR with no hours gets binned. It is alarming the amount of cover letters starting with "will fly for free" or "will pay for TR". Plenty of bean counters out there taking advantage of this, but why would I assist someone like that to enter our profession only to erode my TnC's eventually?
If an FO enters our profession to fly for free they won't have much leverage demanding market rates once they move to the left seat.