The commitment usually has to exist before the application can succeed, but committing without any conditionality means the money is gone whether or not the application does. The common answer is a signed agreement with funds held in escrow and released on approval, prepared with counsel before signature rather than after.
Sequence the deal and the application together
The sequencing problem is real and has a standard solution. Applying with nothing committed produces an application about an intention. Closing outright first puts the whole purchase price at risk of an unfavourable decision.
An agreement that is binding but with completion conditioned on the immigration outcome, with the price in escrow, satisfies the commitment requirement while preserving a defined exit. The terms of that escrow have to be drafted carefully, because a condition drawn too widely turns the arrangement back into a recoverable deposit. Hypothetical example: the buyer of a feed-supplement blending business signs an unconditional agreement with a closing date six weeks away and only then asks how long an application takes; the deal will complete either way, and the sequencing question that should have shaped the contract has already been answered by the calendar.
The escrow terms and the application timetable should be drafted by people who are speaking to each other rather than in separate offices.