The out-of-pocket money on a single deal is small, and it isn't zero. The earnest money deposit is the main item, and on a wholesale contract that's often $100 to $1,000 rather than the 1 to 3 percent a retail buyer might put down. Some sellers accept $10 as consideration. Whether that holds up depends on your state's contract law and the seller's willingness, so a low deposit is a negotiation, not a right.
Earnest money usually sits with the title company or closing attorney, and if you cancel inside your inspection window it typically comes back. If you blow past that window and then walk, you lose it. That deposit is the real cost of being wrong about a house.
Beyond that, a title search costs somewhere around $150 to $400 depending on the state and who does it, and many wholesalers don't pay for it directly because the title company earns its fee at closing. Contract review by an attorney is the one I'd budget for, a few hundred dollars once, since you'll reuse the same forms.
What eats more cash than any of that is finding the seller in the first place. Skip tracing, list pulls, a dialer, mailers at fifty cents to a dollar per piece. People routinely spend more on marketing over three months than they put at risk on any single contract.
The thing that sinks new wholesalers isn't the deposit, it's having no buyer. If your inspection window runs out and nobody wants the contract, your choice is to close yourself or cancel. Line up cash buyers before you lock anything up.