@William Goodman
like Joseph said there is a tremendous amount of contract floating around. If you haven't gotten a an attorney yet then best to get 1 asap. Seek an attorney that is familiar with wholesale contract and representation. 2ndly, share your contract with him and make sure that language/verbage is safe for you contractual and obligational wise. Also you want to make sure that contract doesn't violate any laws from your particular state.
Once you have the green light from your attorney I would sign with any seller at the right price and what the safeguards in place just in case you can't find a buyer in time or at all.
I would then market the deal if you dont have any available buyers. Most investors know and understand the process but not all sellers . Some sellers would be totally against the fact of you making a profit after you negotiate then down on a price. On the other some sellers would not care what you do as long as you can pay the agreed amount by the speciified date. You should know what kind of seller you have on your hands from your interactions.
Ultimately its up you to establish your wholesale model to be 100 transparent with buyers and sellers,
There are arguments of how each 1 of the best option....
Hope I was able to help... Good luck with your endeavors.