I found a way to do a similar thing here in New Zealand. Once I had my PPL and an R44 rating, I decided to continue through to CPL with a 141 school that also had a charter division. I acted as ground crew on the weekends and in return was rewarded with ferry flying, to and from remote bases. For about 4-5 hrs of being ground crew I would normally log a 0.8 or 0.9 of ferry flying. No money changed hands. As with Hughes500's offer everyone saw it as a win win. The machine had to get from A-B, the commercial pilot got paid regardless, I built valuable experience both on the ground and in the air, and I helped them get the job done. I built about 25 hrs of my 150hr CPL that way, learnt a lot and enjoyed myself.
I got to know their systems to the point that when I got my CPL, I was put on the books straight away as a (very junior) commercial pilot. It is not a common scenario, and obviously not something you can count on but there are opportunities around. Your best bet is to choose carefully who you are going to train with as thats normally where your first opportunities spring from, and be a good bastard.