It varies from state to state, however you can figure (as a rule of thumb) 30-35% on top of the wage you pay for all the mandatory "fringes" (WC, payroll taxes, unemployment taxes, etc).
Health Insurance (if you go that route) would cost in the area of $400 per month, employee only. $640 per month family (again, just estimates, not gospel).
Then there is the cost to outfit the employee (and not just uniforms)..... tools on the job (even if you have them there is a replacement cost), the cost to do up their paycheck, file the reports, keep records, etc. A nebulous number, but a cost factor just the same.
Safest route is to as whomever does your taxes. An accountant or payroll service should be able to tell you to the exact percentage add-on.