Hello Waide,
Usually wholesale deals won't work with agents. A few reasons why.
1; Agents are looking for buyers who are not looking to assign the contract. They are on a time limit before the listing contract expires and they don't want the property tied up with someone who's not guaranteed to close.
2; If its already been on the market for awhile its more than likely hundreds of investors have already seen the listing. If it's not sold yet there's probably a good reason why.
3; Even if you could get the property under contract the end buyer you have in mind could cut you out of the deal. If it's on the market its easy for the end buyer to find out who the listing agent is and figure out when your contract expires and go directly to them. I'm not saying all buyers will do this but there are some who will. (Having a big buyers list will help avoid this)
This is just a few reasons.. My advice to you would be to look for off market properties.
If you're not sure how to do that there is plenty of free info on this website just go to BP's search bar and search "How do I find off market properties" plenty of free info to get you started.