Worried about double wholesaling potential

[Sam S.]

Here is the story: I put a property under contract and marketed it (great property).  One individual who I know as a wholesaler says that his partner is going to come check out the property.  He sees it and makes an offer for a little more than asking price with no contingencies and a private lender. Throughout this process I asked them multiple times whether they intend to buy for themselves or assign the contract.  They say they will buy for themselves.  I have other cash offers but this is slightly more and they say they will clost on time. He is willing to give me $2000 cash up front but wants a lock box on the property or a set of keys.  The reason given is to have contractors go in and inspect.  I have never given anyone a lock box access before.  Here is my question: am I paranoid for thinking they might be trying to double wholesale?