Substantially before. The requirement is that funds are already irrevocably committed and at risk, so an application filed while the money is still recoverable is filed against incomplete facts.
The order of operations is part of the test
This is the sequencing question that most often surprises first-time investors, because it feels backwards commercially. The category is designed around an investment that has already been made, so the file is built after the lease is signed, the equipment is bought and the business is ready to operate. That exposure is real and should be entered into with commercial advice, not as an immigration technique. Sensible risk management usually means starting with the expenditures that have independent value if the plan changes, keeping the escrow question under professional advice, and not signing multi-year commitments that only make sense if the visa issues. Build the timeline backwards from an operating start date and treat the application as the last step.
Hypothetical example: a marine-repair shop investor wants to open before the busy season, yet the seller has not transferred the lease or customer contracts. Sequence the deal so that every commitment, contingency and operational record can be understood together. The first review should list which approvals are needed before payment becomes irreversible and which can occur only after closing. It should also reserve time to trace the funds from source through every account. A seasonal opening date does not justify an application filed while the enterprise remains only prospective or while the applicant has no documented ability to direct its daily operations.