Immigration Help Request Post

I am currently transiting in Hong Kong and preparing to go to the United States. My education level is not very high, and I want to find a job after arriving. A friend recommended that I try real estate sales. I would like to ask friends with experience: To do real estate sales in the United States, must I first obtain a license or relevant certification before I can work? Does anyone know whether the requirements vary greatly from state to state? Also, will there be additional restrictions related to immigration status or work visas? I would appreciate it if experienced seniors could share some information. Thank you very much.