The field 'Property__c' either does not exists on the Offer__c object or it is not a Master-Detail relationship.

  Created the custom object (Property) successfully. When attempting the next step, 

Step 3: Goto custom object offer__c

Choose Master-Detail Relationship and 

click Next. For Related To, 

choose Property. Click Next.

Property is not an option in my Master Detail Relationship ... does someone have an explanation or solution?