I am Canadian, and I am Looking to purchase a business in the USA.
1) Technically you can own any business in the US or shares of a US business, as long as the entity is not an S-Corporation (its restricted to be owned by US-persons only). You don’t need any special documents – a purchase contract should suffice, but I recommend hiring an attorney who could assist you with the purchase.
2) I think that is a question best asked to an immigration attorney, or to the Immigration department itself. A far as I know you can obtain a business visa that permits you to be in the US for up to 3 months, but unfortunately I am not a specialist on immigration law regarding visas to give you a clear advisable answer.
3) Once you have decided what state you wanted to form your company in, along with which entity type, you could either file all the necessary paperwork with the appropriate local, state and federal departments, or if you wanted we could prepare and file everything for you.
I hope this answer was of some assistance.
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