If you come into the U.S. with an H1B visa and after a while want to go into business, what is the legal procedure, how does it affect you and how does it affect your employer?

Not much effect with your employer but it will definitely effect you if they know that you are starting your own business, the chance that the employer sponsor your green card would be equivalent to zero.

Thank you very much. To break it down, my daughter is in the U.S. on h1b visa and she has only been with her employer for a few months. Now, she is interested in exporting business (fron U.S. to some other country). As this would involve a lot of time sourcing out products in the U.S. and travelling out sometimes for clearing of the goods, she is confused as to what to do.
My next question then is, is it okay for her to work as ''per diem'' with her employers instead of full time? Would she still be qualified to be on h1b and subsequently get her green card?

H-1B or other employment visas are subject to full time employment only. No part-time or per diem.

If she is interested in doing business in US, why not look into investor visa. She can invest $500,000 as partner or $1,000,000 as sole propriety. These two are in investor visa category. Discuss this matter with the attorney as there are a lot of details and procedures are much different from H-1B.

Thank you once again. If I have any further questions regarding this topic, I'll let you know.