When I had my large piece of land, I always trimmed my own tree line. Additionally, I ocassionally worked with a couple area farmers cutting trees along the edges of their land, just to have the firewood.
Nowadays, I see more farmers using giant batwing mowers to knarl stuff with giant blades, up to like 20 or 25 feet high. Those have quite a long reach. They even do ditch banks with it.
Or they use a front end loader to shove stuff around, and if its a tough one, they use an excavator. They usually do it in the Winter to avoid compaction, so they don't get lines in their beans.
About the only time they really really need a saw guy on the ground, is working ahead of an excavator on a ditch bank. Best to simply cut the trees and have the excavator pluck them out, leaving the root balls intact on the ditch bank. Helps keep the soil from eroding.
I should probably just ask around to see if anybody wants a guy on the ground cutting tree lines.