Strictly, wholesaling means you sign a purchase contract with the seller and then sell your rights under that contract to an end buyer for a fee, called an assignment fee. You never take title. Loosely, people also call a double close wholesaling, and that's different: you actually buy the property and resell it, usually the same day, using short term funding. The house is yours for a few minutes, so you pay closing costs twice and you need money for the buy side.
So the cash out, roughly in order. Data and outreach come first, because you can't assign a contract you don't have. Then earnest money when a seller signs, commonly a few hundred to a thousand dollars, though the amount is whatever you negotiate and whatever local practice expects. Then the walkthrough that lantern described. Then, only if you double close, the funding cost and the second set of closing costs.
Assignment doesn't hide the fee. In a plain assignment the fee usually shows on the settlement statement, and a growing number of states require you to tell the seller in writing that you're selling the contract rather than buying, with the exact wording and timing set by that state's own rules. Confirm what your state and the property's state require with an attorney licensed there.
The part that surprises people funding this is that the buyer side is the constraint. A signed contract with no buyer is just an obligation with a deadline on it.