Lester, what wholesalers usually do is sell to other investors, dealing with the public would be a can of worms.
Find the rehab guys, the landlords or others buying investment properties.
Fin out what they want to buy, like a 3/2/2 in a price range, ask what they won't buy or where.
Now you have an idea of what you're looking for, find it, if you know the buyers needs, what they will buy.
Inform the seller of what you might do, id I don't buy, do you care if someone I know buys it? They don't care who buys. Contract, then bring your buyers. If the buy you're in the money.
If they don't buy, don't use some sham crap excuse, tell them it doesn't meet your investment requirements. That time could be a week with that contract contingency, be up front, or use an option and assign the option taking the buyer into a contract.
This way, 1. you're off deceiving an owner, 2. You don't hold his property off the market while you go beat bushes and come up empty handed. If you do that, you're screwing the owner over as they could have sold to another real buyer instead of messing with you for 60 days.
Wholesaling done right is a quick process, get it done in days, not weeks or months, you can get your money on an assignment and get out of the way. Most real buyers don't need you, except to find a property at an agreeable price. While that isn't always easy, in real estate operations and dealings, it is easy......just understand, it's not easy.
Find your buyers first, then you could go through lists, mail for interest in selling, if they are, match what they have to your customer's needs, if you have a hit, go talk to them, if they don't meet buyer's needs, put them in a slot for future contacts when you find a buyer interested in that type of property. That is part of your prospective inventory.
Don't put owners under some contract when they need to sell and run off beating the bushes to see if you can find a buyer.......that is the wrong way to do this business! :)