This is the message i keep getting even though i deleted the records:
You cannot create a new Master-Detail relationship on an existing custom object if records already exist. You must first create a Lookup relationship, populate the lookup field with data in all records, and then change the relationship type to Master-Detail.
Help
After looking at the screenshot share above, I think you are doing opposite what is expected here. Currently on Property object you have created Property__c field which is Child of Offer__c object in Master-detail relationship, but if you read the error message carefully 'The field 'Property__c' either does not exist on the Offer__c object or it is not a Master-Detail relationship'
The field Property__c is expected on Offer__c object Not on Property object
