No. The official sequence is fee, vetting, then gift. Do not liquidate land or move large sums until vetting is complete and the official instruction to make the gift arrives, and settle the tax timing of any sale with an adviser first.
Sell on the government's instruction, not on the plan
Because the gift is requested only after successful vetting, there is no reason to sell farmland merely because the processing fee has been paid. Selling early exposes the farmer to two risks: the application may not succeed, leaving him with a nonrefundable fee and land he did not need to sell, and the sale may fall into a tax year that is worse for him than the following one. The practical order is: decide with a tax adviser whether permanent residence is wanted at all; submit the online application and processing fee; follow USCIS's email instructions to complete Form I-140G with supporting documents; complete vetting; make the gift only when officially instructed; and complete the remaining immigrant-visa or adjustment process.
Keep the fee, the gift and the visa fees as three separate transactions in the records. Advertised processing expectations are not guarantees, and visa availability can affect when residence is actually granted, so the winter he first hopes to spend south should not be planned around the application date.