The floor is roughly the cost of reaching people, and you can get that quite low if you're willing to spend time instead.
What you actually need to buy is contact information and a way to deliver a message. Driving an area and pulling owner names off the county assessor's site costs nothing but hours, and most county property records are free to search. Skip tracing individual owners can be bought a record at a time rather than by subscription, which turns a fixed monthly bill into a variable cost you control. A few hundred dollars, spent that way, buys you a couple hundred conversations attempted. That's a real experiment.
What that money can't buy is the closing. Wholesaling means you get a property under contract at a price, then assign that contract, meaning you transfer your right to buy it, to another investor for a fee. You don't need purchase funds because you never own the property. You do need a buyer who's ready, and finding that buyer usually takes longer than beginners expect. Whether an assignment is permitted, and how it has to be disclosed, varies by state and some states regulate it directly, so ask a local real estate attorney before you sign anything with the word assignment in it.
The part that catches people at your stage is that the seller conversation isn't the hard skill. Knowing what the house is worth and what it costs to fix is the hard skill, and that's why @girder's point about repair estimating matters more than which platform you subscribe to. A number you can't defend gets you a contract you can't assign.
