Multi-decade time frame required to complete grad study? If you have a master's degree already then you only need two more years for a Ph.D (in most cases - or at least both of my parents did and I highly doubt they were both abnormally fast).
Are you solely working on the start-up? I would suggest going about your business without the need to incorporate right away. A lot of people waste a lot of time and money incorporating when they have no idea if the product can be built, is desired in the market place, or validated.
My suggestion would be to come to the U.S for your Ph.D (if visa requirements allow you to do so). You will have two years to work on your studies and then also validate your startup idea in the U.S, which may be more friendly in terms of validation and (if you moved to startup hubs) could be useful in terms of incorporating and scaling.
Whatever you decide to do, best of luck!
