What kind of business relationship do you have with your Realtor? Does your Realtor represent you as 'Buyer's Agent'? If so, sign a Consumer Information Statement.
Now if the subject property is an 'Office Exclusive,' your Realtor may be out of luck regarding a commission. May I suggest negotiating a 'referral fee' in any case?
Our realtor formally and legally represents us as a buyer’s agent. We signed all the legal paperwork before we submitted an offer.