You should retain EB-5 counsel, securities counsel, a business planner, an economist, and possibly develop a relationship with an immigration broker. Starting from scratch, you may be looking at more than $100,000 in professional fees and filing fees, but each situation is different.
Every case and representation is different. The first step is to consult with an experienced EB-5 attorney and discuss your project goals, timelines, funding, and budgets. Then fees and costs can be determined.