50 dollars an hour is fair, the trick is knowing how many hours it will take to deal with brush. You can run a tree service without a chipper/dump, it's just a royal pain in the ass. I'm doing it right now, and as soon as I get the capital to buy a chip dump set up I will. You can't do it with just a pickup though, you at least need a trailer. A sixteen to twenty foot lowboy works good, and you gotta be real methodical about stacking the brush. I find butt ends facing forward works best, cut often to get it to lay down flat, and tie the whole load down with ratchet straps. It's amazing how much brush you can stack this way, and with a little practice, it's almost as fast as feeding a chipper, Oh but GOD it's a pain! The real pain is unloading! You get a bunch of dry brittle tangly crap all compressed and mixed together and it will take some time. And if you have to go to the dump with it your pretty much at the mercy of the dump hours. I live on a farm personally I dump all my brush in the middle of my field and burn it. I lay a big choker strap down on the bottom of my flatbed and load brush ontop, that way I can hook the whole load up to my tractor and pull it off. Still a royal pain in the ass. and the brush adds up oh so fast, the time it takes to drive back and forth, and the gas money, all adds up fast too. Then you'll find that 90% of the estimates will probably be for removals, and what does that equal?, a hell of a lot of brush. I don't mean to be discouraging in the slightest, just be prepared, without a chipper/ dump, the brush is biggest obstacle to being a viable business. Even if you rent a chipper, unless they want a pile of chips blown onto their lawn, you need something to blow them into, and shoveling chips out by hand is worse than unloading brush by hand.
The key to survival in this situation, is to do quality work. If the customer wants to pay you to haul all the brush away by hand, leave their yard spotless, Don't drive on their lawns, and most of all, don't screw up their trees. Learn the difference between good prune cuts and bad prune cuts, Don't gaff up trees unless it's a removal, ( or don't let climbers you may hire gaff trees...) This type of reputation can set you apart, and people will be willing to pay a little more if you have a good reputation, which will help cover the cost of loading hauling and unloading that impossible tangle of god forsaken brush youve got attached to your pickup truck.