I have two great resourses for dumping mulch.
#1- My home. I'm 2 minutes away from town. And I'm zoned agriculture. I have farmers & gardeners taking mulch away all the time. It's great P.R. (It is one major reason I decided to buy the home I did. The convenience to dump right here is second to none).
#2-There is a large landscape supply place in the heart of town that takes all tree service mulch free. They will sell our mulch at $7/cubic yard (if I remember right). But, the biggest incentive for them is regrinding it and coloring it.
I use to sell some loads. I sold a load for $30 dollars, but then started to sell it at $50 dollars. If I were to do it again, I'll sell it for $135/load. That would be nearly 20 cubic yards.
My thing is this: I feel that if I'm going to sell a load of mulch, I want to give them the best we can create. I don't want a reputation of selling stringing Elm or something with thorns.
My model 90 makes nice uniform chips at about 3/4" x 3/4". It would be playground quality (if I could get out the smaller twigs.
With that said, I have to time the delivery after a tree removal that can fill the truck. This way the majority of the chips came from log wood, hence, creating the nice chips. This also means I need to have good knives on...
This means that I have to keep a small list of mulch deliveries and wait until I have "the good stuff." It is so much of a pain, that I stopped delivering/selling last year. (FWIW, I only sold about 4-5 loads per year, so it wasn't much).