For the most part, Lenders force REO Brokers to take smaller than normal commissions, so I wouldn't say that the broker is greedy. They may simply be trying to survive.
I never take an unsigned buyer into a property. Think about it for a minute. Why should I make a committment to a customer who is not willing to make a committment to me? Should I waste my time, effort, wear and tear on my vehicle, gas, postage, printing costs, phone minutes, etc showing homes to someone who doesn't want to hire me? It just doesn't make good business sense. Of couse, I provide an "Easy EXIT" if the client is not satisfied with my work, at any time before we sign a Purchase Agreement, they can cancel their contact without obligation. And I've never had anyone cancel yet!
The questions of insurance and business liability come into play as well. What would happen if you fell down and were hurt in a REO home? Who would you sue? The bank has a whole department full of lawyers. Would you sue the real estate agent who showed you the home?
In the case of an REO, you really should hire a Realtor to represent you as a Buyer's Agent. There are so many things that you can get stuck with and some of them aren't even legal in the state of Minnesota. We are so very different from most other states and Lenders are not keenly aware of our laws. Just the other day I wrote an offer to purchase a REO property and I had to change 7 items on the Seller's Addendum (required) because they were either illegal, against the MLS rules, uncustomary, or simply not in my Buyer's best interest.
The Seller (Lender) said that the Buyer must use the Seller's Title Company... NOT!
The Seller (Lender) said that the Buyer must pay to de-winterize the home for the inspection... NOT!
The Seller (Lender) said that the Buyer must pay to re-key the home after closing... NOT!
The Seller (Lender) said that the Buyer must pay for the Owner's Title Insurance Policy... NOT!
The Seller (Lender) said that the Buyer must pay for all mortgage required repairs... NOT!
The Seller (Lender) said that the Buyer must pay for all levied assessments... NOT!
The Seller (Lender) said that the Buyer must pay for all pending assessments... NOT!
There is a lot more to buying a REO than just making an offer. You really need to be protected and a Realtor isn't going to charge you for their services because they will be paid by the Listing Broker.
You may also be confusing a "Disclosure" with a "Contract". Minnesota Law REQUIRES all real estate agents to explain agency to you and have you sign the "Agency Relationships in Real Estate Transactions" disclosure form "at first substantial contact" with all customers. That is completely different than the "Exclusive Right to Represent Buyert" contract.