How To Protect the Deal??

When buying REO properties or any property for that matter that has a large amount of equity, the prospective buyers offer more and buy the deal.

How can one protect the deal if you do not have the money to buy the property out right for cash?

The bank sends me a counter-proposal agreement saying that my offer is accepted.
I then sign the agreement and send earnest money deposit to the agent.
When I send prospective buyers to the real estate agent to view the property, the agent makes them another offer and cuts me out of the deal.
How are other investors getting around this situation?

never let the buyer and realtor meet. become friends with another realtor so that you can get access to the lock boxes

You also have a contract, so I don’t see why the situation you mentioned would occur