Let's say that a foreigner wants to sell products or services in US using a company there to save his/her clients of importing his products/services. Yet this hypothetical entrepreneur does not stay in US all the time, only when he goes to sell his products/services under a business visa. Which are the rules of such operation?
You cannot work for a US Company on a B1 visa, that would require a work permit (H1B). Of course you can set up a US company, but I don't see the advantage in your scenario, it would only make sense if the company would have employees in the US. As a rule of thumb a B1 visa only allows you to do non-manual labor, like attending meetings, soliciting sales, negotiating contracts etc. You cannot run a business or get paid by your US business.
What kind of products are you selling? It should be relatively easy to just ship them from overseas using a courier service.