there is no best answer. It depends on the circumstances of the particular business. Sounds like you are looking to make a substantial investment. it would be worth your while to make some of that investment in an experienced business immigration attorney.
You need to speak to a competent tax attorney who has experience in the areas of international taxation. There are a number of different issues, each of which involves various trade-offs, so it's impossible for anyone to give you a good answer to your question without actually having a consultation with you.
My answer does not constitute legal advice and may not be relied upon by anyone for any purpose and does not constitute an attorney/client relationship or an offer to form such a relationship. This disclaimer is intended to be fully compliant with the requirements of Treasury Department Circular 230 and the terms thereof are fully incorporated by reference. If you wish to consult with me please contact me at dana@nytaxcounsel or visit my website at www.nytaxcounsel.com
The knee-jerk answer is that an LLC is the best structure for the business that you describe. However, as the fine gentleman (Dana) indicates, there are many factors that could lead to a different conclusion, e.g., a "C" corporation (a blocker entity); an LLC owned by "C" corporations. So, if you want to get the correct answer, you cannot get it over the internet. You need to walk in to the office of a competent international tax attorney in Phoenix - a city rich with highly skilled tax lawyers - and buy a few hours of time. If you are spending $500,000 on the business, you can afford $5,000 to analyze the best approach and set it up properly.