@Jim Witten, do not sign any form of a listing agreement with this real estate agent. First, yes, this is a very common form of agent marketing. Any agent can say that they have an all-cash buyer for your property, but at what price? I personally have $100 cash ready to buy your property right now.
Second, no, the open ended listing agreement suggested by some on here is not appropriate because that would mean that you think that the agent is actually representing you - dual representation - which is not beneficial to you and should not be legal, in my opinion.
Tell the agent to provide you with the all-cash written offer for your consideration. The customary California purchase agreement includes a contingency for the physical inspection of the property, so you will grant the buyer and agent access to inspect the property during the contingency period. You can also tell the agent to write into the contract that you will pay him 2-3% of the sales price, upon a successful closing. The only reason that he wants to list the property is to try and double-end the transaction, allegedly represent both sides (not possible), and get 5-6% as commission. And, if it doesn't sell in 7 days, the agent will tell you that it's the fault of the property or your unrealistic price expectations.