Substantiality is measured against the cost of this business, not against a fixed figure. A buyer paying the full price for an operating company with employees is normally on solid ground, provided the funds are irrevocably committed.
Proportion decides substantiality
There is no minimum dollar amount. The test compares what has been invested with what it costs to buy or establish this particular enterprise, and a purchase at arm's length for the whole of a going concern generally satisfies it, because the amount invested is by definition the cost. Difficulties come from what has not yet been spent. A deposit sitting in a lawyer's trust account remains uncommitted if the buyer can reclaim it at will; however, a purchase conditioned only on E-2 visa issuance may still qualify when the funds are escrowed for release upon issuance and the buyer is otherwise obligated to close. Working capital held in the company's own account for the operating plan counts when the plan explains what it is for. Present a schedule that shows every dollar, where it is now and what commits it, and be candid about anything still conditional.
Hypothetical example: a Canadian couple buys a mobile diagnostic-imaging service and leaves part of the price in a contract that is refundable if the visa is denied. The first review should list each payment, its release condition and the business asset it acquires. The purchase agreement, escrow terms and paid invoices settle whether the capital is irrevocably committed and at risk. Restructure the transaction before filing if the buyer can simply recover the essential funds after a refusal; a large account balance is not a substitute for a binding commercial exposure.