Being a jockey manager isn't a licence to print money, the ones that have no other residual income probably need to have a punt to get by. If you took it at say $ 10 of every riding fee charged to your jockey, plus say % 5 of whatever stake money they earn, you'd need a few big stake wins to better the average wage. Personally, sitting watching hours of race videos every day would end up sending you nuts, throw in aggro from some trainers plenty of easier ways to make a living.