There is no set amount. Substantiality is measured in proportion to the total cost of purchasing or creating this type of enterprise, so a service business with modest capital needs is judged against that cost rather than against a general figure.
Proportion, not a number someone quoted
Hypothetical example: the buyers hear a figure repeated at a trade show and treat it as a threshold. The correct approach is to establish what it actually costs to acquire this business — purchase price, vehicles, tools, inventory, bonding, initial working capital — and to show that the amount committed is substantial relative to that total. A small service company can qualify on a smaller investment than a manufacturing plant.
Separate committed capital from future operating expenses: a five-year lease estimate is not invested capital. Then handle marginality: the enterprise must have the present or future capacity to generate more than a minimal living for the investors and their families, or to make a significant economic contribution, and the nine existing employees are relevant evidence. Government amounts for the application itself are published by the responsible agency and are small beside the transaction.