Neither extreme is safe. Closing outright before a visa exists puts the money at risk with no status to run the business, while an unsigned deal shows no commitment. The usual middle path is a signed agreement with funds in escrow released on visa issuance, then closing immediately after.
Structure the closing so the commitment and the status arrive together
Consular officers expect to see funds irrevocably committed, and they accept escrow arrangements that release on visa issuance because the buyer cannot recover the money simply by changing their mind. Negotiate that structure into the purchase agreement from the start, with the seller's consent to a closing date that follows the visa decision and a defined outcome if the visa is refused. Meanwhile, the U.S.
corporation should be formed, the business bank account opened and the lease assigned or a new one signed, so the enterprise exists as a legal entity able to receive the assets. Book the consular appointment once the executed documents and the money trail are complete; check current appointment availability at the post, since waits vary. The family should not sell the Québec rental duplex or resign from other income before the visa exists, because the line of credit and the security behind it are part of the case.