Since you're thinking about getting into QR Codes with Realtors.....you might want to consider selling them Business Cards with QR Codes printed on them.

Take a look at this site;...
http://www.plasticprinters.com/QR_Code_Business_Cards/

You don't have to do Plastic Cards. You can get Biz Cards printed OnLine for less than $35 per 500 and.....charge $185 for 500 WITH the QR Code....for a nice profit of $150 for you Time!