A business visa is required. Upon arrival, the hiring company will typically begin the process to convert your business visa to a work visa. Business visas are typically valid for one year and you must leave the country every 60 days. To (my) knowledge, as long as the exit date stamp and the next entry date stamp are on different calendar days, then you are allowed back into the country in good standing for another 60 days. Work visas are valid for one year and do not require you to leave.
There are no licensing bodies that I am aware of. Step 1: The undergrad and doctorate schools you went to need to give you a certified copy of your diplomas. Also get your state licensing board to send you a certified copy of your license. Step 2: Then you send those certified copies to your secretary of state office based on the state they were issued. for example: Texas diploma goes to Texas Secretary of State (even if you live in Kansas). This department certifies and "stamps" that the person at school who certified your documents are in good standing and this paperwork is now officially recognized by your state. Step 3: All these documents along with the forms that China wants before issuing you a business visa (and whatever else their website requests) is brought in person to the China Consulate that regulates your state. Here all these documents get an Official People's Republic of China stamp and seal verifying that these documents are real and approved. The person applying for a visa doesn't have to be the one submitting the document, companies are available to do it for you. For example: mail you documents to a company in Houston and a representative goes to the Houston Consulate Location and submits the documents for you. It is quite easy but every office has a fee and processing time of several weeks typically. Obviously if you are not from the US, you need to insert your appropriate country's equivalents into the above