Generally, all states who have sales tax also have a use tax, and certain labor and services are taxed. However, which labor and services may very from state to state.
The only states who do not have a sales and use tax are: Alaska, Delaware, Hawaii, Montana, New Hapshire, and Oregon.
Hawaii charges an excise tax in lieu of a sales tax.
For this reason, I recommend registering in each state, and obtaining a sales tax certificate. Then use the following software to help do your taxes:
All states except the ones listed charge tax on labor.
The states that you are concerned about, North and South Carolina, Virginia, New York, New Jersey, Penn, Delaware, Maryland, Tennessee, Georgia, Alabama, Florida, West Virginia, Louisiana and Texas, all charge sales tax on labor, including the conditions of the contracts that you are concerend about.
However, the detail of information you want requires about 12 to 18 hours of research.