I agree with the advice to figure out how much you need to make per hour to make it worth your while. We pay subs more than that per lawn, but I don't know if what we pay is even close to average. For us, it keeps our best and favorite guys working and we make just enough off the top to make it worth our while.
Keep in mind that the number of properties offered initially may decrease over time as properties are sold off, we have seen that happen and it caused a few bumps in the road in trying to keep it a worthwhile effort for all parties. It will be different everywhere (here we have seen more properties get dropped from the list than new ones come on) but the consistency of the volume of properties is a question you may want to ask.