Good organic compost material shouldn't be too hard to find.
You should look at your local trash/recycle collecting company. If they pick up yard waste (grass clippings, leaves, branches, and those brown paper bags) then they will most likely make organic compost waste.
Then all you have to do, is contact your local trash/recycle company and they will tell you where you will need to go to pick up their organic compost.
You will need containers and maybe a shovel.....unless you have a dump trailer. If you have a dump trailer or empty truck bed....then they will use an end-loader and dump it in usually free.
The trash/recycle company should also get their compost checked at least once a year, because you want to make sure there is nothing toxic/bad going into your yard or any future customer's yards.
The trash/recycle company should be able to send you copy of their soil test. And then, you can use their soil test to show your customer's that the organic compost is good and safe for their yards.
Our local waste management company starts selling organic compost in March. They usually have a few storage buildings full with organic compost, until they can start collecting yard waste bags.....then they start their process all over.
2013 Ford F450 Super Duty Truck
2010 Exmark Lazer Z 60" deck
2012 ExMark 30" Riding Aerator
2011 Lawn Solution Dual Hyrdo Aerator 24"
2011 Echo(backpack blower), (hand blower), (chain saw), (hedge trimmer), (string trimmers), & (tree pruner)
Craftsman 4.0 edger
2007 Big Tex 4ft metal high side 7' x 12' Trailer
2012 PJ 7' x 16' Dump Trailer
2012 Ecolawn Applicator model 200 Compost Spreader
2012 BillyGoat Force 13 Wheeled Blower & MV650SPH Commercial Vacuum