There is no fixed amount. The test is whether the committed capital is substantial in proportion to the total cost of purchasing or establishing this specific enterprise, which means the answer changes with the business.
Build the proportion, not a number
Start by fixing the denominator: what would it cost to buy or create this business? For an existing tree-care company with crews, vehicles and a customer base, the purchase price is the natural figure, supported by the asset schedule and any valuation obtained for the transaction. Then set out the numerator: funds actually and irrevocably committed. A purchase where most of the price is paid and the remainder is a genuine, secured obligation reads differently from one where a small deposit is at risk and the rest is contingent. Because the standard is proportional, a modest-cost service business generally needs a very high proportion committed, approaching the whole cost, while a capital-heavy operation may support a lower proportion. Comparing your figure to what someone else invested in a different industry tells you nothing about your own case.
Hypothetical example: A ceramic-studio buyer plans to purchase an operating American workshop and retain two instructors. The first review should produce a treaty-nationality record, a full purchase-cost schedule, and a management plan showing how the buyer will develop and direct the enterprise. Passport evidence settles nationality; ownership records settle enterprise nationality; the signed acquisition documents settle the cost and commitment. Funds must be committed in a manner that exposes them to commercial loss, not left freely recoverable in a personal account. The enterprise must be real and nonmarginal, meaning its capacity must go beyond supporting the investor's own household. E-2 itself does not provide a built-in permanent-residence path.