I'd say get in with whomever cuts the biggest checks. Listen to everyone's advice, and make a daily commitment to research. There are so many conflicting ideas and concepts that you'll wonder what in the world the truth is.
Be aware big egos, winning and complaints are prevalent in this industry and they will absolutely effect the information you get.
I'd say the real issue with heavy haul is if your not the owner of the company dont expect the income to be a dramatic increase. If you are the owner expect extreme equipment, permit, and maintenance expenses.
Like all things if you sincerely desire to do it, do it. To hell with what everyone else says.