I am undergoing massive problems of this nature right now. Our contractor appears honest, but our interior designer does not.
My advice is the following:
NEVER pay the entire amount until you are in agreement that the job is done to your satisfaction. Dole it out as you go along, and make them fix any problems before giving them the final payment.
Get a completion bond.
Be present at the construction site as close to constantly as you can.
If necessary, hire an expert to come in and review the progress on a regular basis. You will save twenty times what you would have had to pay to fix problems after construction has been done incorrectly. And don't let the person who fouled it up charge you to do it again--in fact, inform them that the additional costs will be borne by them. Be a little careful about that while construction is ongoing, because some of them will try to extort you by threatening to quit the project if you make them pay for THEIR mistakes. I've had to have a lawyer write a letter to subs who tried that.
I could go on and on, but I am presently fighting with the supply company who provided me with ten interior doors that don't match each other dimensionally, do not conform with their frames, and had sawdust accumulated in their grooves, which was just painted over at the factory. Plus, they were supposed to be treated, and one surface of them was not.
Edit: There is no way I would employ a person who is in another state than the one where the building is located. Too hard to come down on them if they screw it up.