My brother-in-law in India wants to open(register) an IT company in US. Is that possible? How?
And if now, then I'm here in US with a student visa. Can I register an IT company in USA and help him starting up business from here?
You should decide in what state you want the company registered (each state has its own set of rules and requirements), and work from there.
As a student on a student visa, you're not allowed to be employed. So you can help with filling the forms and writing the checks, but you cannot be an employee.
Agent services would probably be required. Check the selected State's Secretary of State (or Department of Corporations, or other corporation regulatory entity) for specifics.
Note that once registered in the US, the company will have to file taxes both to the IRS and the State in which its registered.
There are several requirements your brother-in-law will have to take into account:
Tax reporting is perhaps the most complicated part of being an foreign owner of a US business. You will probably want to consult an expert on this process. For more discussion on that issue, see: http://www.hawcpa.com/_home/feature_never_wanted_to_know.asp, http://www.groco.com/readingroom/atax_02.aspx,
3.Registered agent - This depends on the type of business entity you wish to establish in the US. Each entity type determines whether you have personal liability and also the way it is taxed. Two predominant business entity types are the Corporation and the Limited Liability Company (LLC). You need a registered agent in the US state of your choosing to establish either of those entities. You can, however, avoid the registered agent requirement if the business operates as a sole proprietorship or general partnership with unlimited liability (meaning your personal assets are accessible in a lawsuit).