Don't forget to figure in everything, tools, licensing fees, liability insurance, truck insurance, health insurance, gas, vehicle depreciation, Medicare (you will now pay it all yourself), income tax, state sales tax, city sales tax, sick pay, retirement savings, holiday pay. Don't forget for every billable hour there will be associated non billable time like getting bids, figuring bids, supply house runs, book keeping, invoicing. There's more of course but I think you get the point.
Don't be one of the guys who thinks he's gonna get rich on $35.00 hr. Don't cheat yourself out of a retirement.
It's a tough road, but if you have what it takes, the reward is there. Just be sure you know your true costs, both financially and personally.