Very old thread.. You can look around here there is a bunch of info out there. That gross number would be trailer and truck. If your really going to set up a business for your kid, Do it right and get a flat bed/stake truck and mount it all on that. Make sure you get diaphragm pump and air compressor rig.
Call your local insurance agent it varies so much its crazy. I pay 800 a year that's for general liability, but you need commercial car insurance its illegal to do business in personal vehicles. Also with there being a partner situation your going to need workers comp. Lastly if you have all this invested why in the world would you risk it all PLUS your personal assets if they **** up ??? Make sure you understand fully what you have to risk when doing businesses.
With a LLC the only thing that can be sued is the business.
Good luck I hope they appreciate what your doing for them!