My former employer used to pay me minimum wage, based on working 8 til 6 4 days per week. For that I was expected to fly between circa 30 hours and 50 hours per month (seasonal variation) before I started earning "flight pay". In return we were expected to be on the company premises "working" for the duration of our working day come wind, rain, hurricanes etc.
Worked well for me because I could count on getting a stable salary every month in winter and summer, and occasionally could earn a bit extra. Drawbacks were mainly in deep winter when you would be faced with 10 very bored FIs with nothing to do sitting around for 10 hours, sometimes for 2 weeks at a time.
The company believed they were compelled to do this by the minimum wage leglislation, felt they were doing the right thing by their staff and expected all other flying schools to act in a similar manner. Sadly I think we were just one of a handful of schools who enacted the leglislation. As a result there was a badly handled attempt at redundancies and now everyone joining is on flight pay only.
Until PPL FIs are prepared to unite and withdraw their services there will never be decent pay in this side of the industry. But there is a ready supply of new FIs who are desperate to get the hours, who will work for a pittance and who would undermine any attempt at fair pay (look at how many pay for a type rating now).