“Substantial” trade must include numerous business transactions over a period of time. The income generated from such transactions must be sufficient to support the applicant and his/her family.
The consular or USCIS officer will not only look into the amount of trade being conducted but also the monetary value of such transactions. A singular transaction of very great value will not be considered substantial trade.
Smaller businesses may qualify if they can demonstrate a history of international trade involving numerous transactions of value in the aggregate, even though if each of those transactions is not high in value.