Buyers agree a closing date before knowing the consular interview date, then must choose between breaching the contract and paying without a visa. Put a visa-issuance condition in the agreement, open escrow early, and let the consular calendar set the closing.
Let the consulate's calendar drive the closing date
The sequence that works is: negotiate the deal with a visa condition, sign, fund the escrow, prepare the business plan and consular forms, submit the application and attend the interview, then close on issuance. The sequence that fails is a seller who insists on a spring closing to capture the season and a buyer who agrees, then finds that interview availability and administrative processing push the decision past that date. Consular wait times vary and are outside anyone's control, so the agreement should tolerate a delayed closing rather than penalize it.
Meanwhile the buyer should not begin operating the business. Managing staff, ordering stock or serving customers before the visa is issued is unauthorized employment, even for an owner. Visiting to inspect the premises and meet the seller as a business visitor is permissible; running the spring season is not.
If the seller cannot wait, consider a management agreement under which the seller's team operates the business through the season on the buyer's behalf, with ownership and control passing at closing.