After. The processing fee is due at application, but the gift follows successful vetting, so nothing forces a sale earlier. Liquidating the practice on the strength of an application alone risks losing the business without gaining residence.
Let the vetting decision, not the application, trigger the sale
The published sequence is application and processing fee first, vetting second, gift third, and immigrant processing under the carrying category last. Each stage is a point at which the case can stop, and the only money at stake before vetting is the processing fee. A veterinarian who sells her practice at the application stage has converted a going concern into cash for a decision that has not been made; if vetting fails or the category's visa availability stalls, she has no practice and no residence. The prudent order is to confirm the current terms, apply and pay the fee, wait for the vetting outcome, and only then arrange the gift, list the practice or negotiate a partner buyout, and begin the state veterinary licensing process in parallel with immigrant processing. Build in the possibility that the official terms change between stages by re-reading the page before each step; a change in amounts or process is a reason to pause, not to accelerate.
Hypothetical example: An optometrist expects to close her practice immediately after submitting a Gold Card application. The first review should distinguish the nonrefundable processing fee, the vetting result, the applicant's gift and the later immigrant steps. A Gold Card payment by an individual applicant is a gift paid by that applicant to the U.S. government; it is not a conventional visa purchase or an investment that can be recovered. The prudent decision is whether to keep the practice sale conditional until vetting and the carrying immigrant process are clear. The official payment instructions and the approval notice, rather than a promotional summary, settle when the next irreversible action is due.