Sign with an escrow or conditional closing, commit the funds, apply, and complete closing on approval. Applying before commitment fails the at-risk test; closing unconditionally before approval risks owning a U.S. business the buyer cannot lawfully run.
Let the escrow clause carry the timing risk
The order of operations resolves a real dilemma. The State Department expects funds to be irrevocably committed before it will issue a visa, but an unconditional purchase leaves the buyer exposed if the application fails. The standard answer is an escrow arrangement: the purchase agreement is signed, the price is deposited with an escrow agent, and release to the seller is conditioned on visa issuance, with the funds returned if the visa is refused.
That arrangement satisfies the commitment requirement because the buyer cannot simply withdraw. Hypothetical example: a Lac-Beauport landscaping contractor agrees to buy a U.S. grounds-maintenance company; the seller initially refuses escrow, then accepts once the buyer offers a larger non-refundable deposit for the seller's inconvenience.
That deposit is at risk and counts toward the investment. Only after visa issuance should the Québec household give notice on leases or sell property, and even then the first admission period and the renewal cycle should be written into the business plan.