Our biggest local guy with mulch business obtained a contract with the city to have the leaves that the city picks up brought to him. He also receives some other stuff from other sources. Don't think he has to go looking for feedstock. He has a big machine or two that mulches and then windrows the stuff, adding the right amount of water, etc. He sells mulch, compost and soil.
Without this sort of deal, I'd think you'd forever be searching for sources.
Check out
Panorama Pay Dirt or something similar.
Ralph