I’ve gotten the same requests too. I have some speculation that its also people that are generating proposals/decks for investors and are just probing for prices to plug into their models. If you really want to vet them, ask for whatever license they hold and set up an escrow account for them to put their money in to prove they are serious buyers. That will send most fake/non serious requests running.
a little blurb on escrow accounts here. How Escrow Protects Parties in Financial Transactions