It's a normal ask. Anyone who does volume gets asked and has the files ready.
What to ask for, in order of how much it tells you. First, two or three closing statements from assignments he's done, sale prices and fee visible, the rest blacked out if he wants. Second, the name and contact of the title company or closing attorney he uses most. Call them and ask whether they close his deals regularly. That call is the single most useful thing you can do and it costs you nothing. Third, a redacted example of a signed assignment agreement with one of his buyers, which shows he has actual buyers rather than a Facebook group.
One thing to keep straight: proof of funds is a letter saying a buyer has money, and transactional funding is short-term money that funds a double close for a day or two. Neither one is evidence he can sell your contract. Closed files are.
Ask him what happens if the deal dies after he's spent time on it and after you've spent money on inspections or an extension. Get the answer in the JV agreement, along with who talks to the seller, who talks to the buyer, and whether your earnest money comes back off the top before the split.
While you're at it, ask which state you're both operating in and whether wholesaling there triggers any licensing or disclosure requirement, since that varies by state and a few have tightened rules specifically around assignments. A real estate attorney in your state is the person to confirm that with.
