Z-Visa: My husband accepted a job for a USA based company

Good Day,

I am hoping someone can help me as I can't seem to find any information elsewhere and I know travelchinaguide is usually quick to respond.

My husband accepted a job for a USA based company but the job is for Tech support within Beijing.
What does he need to do to be able to work in China legally: Which documents does he require, etc.

Your help would be very much appreciated.

Thanks