@Daniel O'Grady If you are paying cash why would you need a rebate? Why not write the offer for that percentage less? However, writing the offer for 3% less now makes you the same net to the seller as a buyer with a buyers agent so you've lost your competitive edge. You could write the offer and then ask for a percentage to cover your closing costs but being cash you wouldn't have much depending on your state. In Utah, the seller pays the title policy so there really aren't many fees unless you want a lenders policy??
You could have your friend who is an attorney write the contract for you.
To answer your question on commission, the seller is paying the agent 5-6% to sell their home. That agent is called the seller's agent. The seller's agent will put the home on the multiple listing service and offer a buyer's agent commission to bring an able, ready and willing buyer to the property. There is no set amount but it's often half of what the listing agent is taking from the seller. In the event of an unrepresented buyer, it's up to the listing agent for what they do as they have the contract with the seller. They can take the full commission as helping an unrepresented buyer is a lot more work than working with another professional. They can reduce their commission for their sellers and give a rebate to the seller. They can't give it to a buyer. However, it could be a credit in closing costs, or a lower purchase price. It's all about the net to the seller.