One correction to how the question is framed. The reason a wholesaler double closes is usually not that a deal needs it structurally. It's that the assignment fee is large enough that the wholesaler doesn't want it disclosed on the settlement statement the buyer sees, or that the buyer's lender won't fund an assigned contract. Those are two different problems and only the second one is really about capital.
Run the numbers before you assume the double close is worth it. On a 90k purchase, transactional funding at 1.5 points plus fees is somewhere around 1,500 to 2,500, and the second closing adds title and recording costs again, so figure 3,000 to 5,000 all in depending on the state and whether that state charges transfer tax twice. If the assignment fee is 8,000, you've given up 3,000 to 5,000 of it, call it half, to avoid a disclosure. If it's 35,000 the math looks different.
What @sable hasn't raised is the deal-level risk of relying on a network member's funding contact. Transactional lenders wire against a scheduled closing. If the end buyer's funds slip a day, and yours have already funded the first leg, you now own a house you intended to own for four hours, with no permanent financing lined up. That's the scenario worth writing down before you use the strategy, and it's why some members with thin reserves stay on assignments only, even at a lower fee.
Whether the seller has to be told about the assignment or the fee varies by state, and a few states have tightened this. Get that answered by an attorney where the property sits, in writing.