Usually labor does not incur sales tax, only material. However, every state is different so you should check with your state. Most of this type of information can be found on your state's department of revenue web site.

Also, I'm assuming you now this part, since you are a contractor and not an employee, at the end of the year you should get a 1099 from this person that shows the amount he has paid you throughout the year. You need to claim that as income and pay income tax on it. Again, depending on your state laws, you are more than likely required to pay estimated income tax on a quarterly basis.