During due diligence, before the purchase agreement is finalised. The transaction documents themselves carry several of the requirements, and they are far easier to shape than to explain.
The agreement is part of the evidence
Hypothetical example: Buyers naturally treat the purchase and the immigration application as sequential projects, and that ordering costs them the chance to influence the strongest evidence they will ever have. The escrow terms, the ownership structure, the management provisions and the description of what the buyer will do are all written during the transaction, and each of them answers a requirement.
Assembling the financial trail is also easier while the funds are moving, since statements and confirmations can be captured as they are generated. A Cavan Monaghan purchaser should therefore treat the due diligence period as the document-gathering period: obtain the target's financial records, settle the ownership arithmetic, draft the escrow with the commitment requirement in view, and record the intended management role in writing before signature rather than describing it afterwards.