A dated copy of the official text, the specific provisions relied on, a record of who said what, and any correspondence — held separately from investment or business documents.
Write down what you were told and by whom
Two records matter. The first is the official text itself, saved with a date, so that any later change is visible rather than invisible. The second, less obvious, is a note of what the household was told, by whom, and when — because if a term proves inaccurate the household will want to know whether it acted on official material or on someone's description of it.
Keeping the file separate from any EB-5 or business documentation is a small discipline that prevents the categories from blurring in the household's own records. It is also worth recording the decisions as they are made: what was decided, on what information, on what date. That record is what makes it possible to re-take a decision cleanly if the terms move.