There was a long thread about this topic somewhere on LS - I don't recall if it was landscaping or lawncare. But anyway a guy was going to hire something like 250 kids as subs, and provide them with equipment to mow. Then there was discussion of whether they were then, in fact, subs.
Run a search to find it in one of those 2 forums.
Other than that I can't be of much help - I do nothing as a sub or with subs.