“My brother has been traveling back and forth to the U.S. with a visa waiver, and always leaves before his 90 day authorized stay is up. He has made several trips to the U.S. in the past three years doing this, without problem. Is this normal? He would like to set up a small business here, but I have told him that someday he could run into problems with immigration.”
"Normal" isn’t a word that always applies to the process of gaining re-admittance to the U.S. A friend who’s a green card holder in good standing was recently detained at JFK Airport by a Customs and Border Patrol agent for questioning, for no particular reason.
And there’s your brother, able to enter whenever he likes with ease. Go figure!
You are correct, though, in advising that sooner or later, if he continues this pattern of travel, questions are going to be asked about his residency and the reason for his frequent trips to the U.S. Creating a business under these conditions isn’t ideal.
It’s also not in keeping with the terms of the visa waiver, which does not allow for employment.