Traversing lookup fields to related record fields

Question

I'm trying to access a contact object field through a related object's lookup field. Billing_contact__c below (2nd td) is an entity object lookup field that has a related contact record. When I reference the Address__c field in the contact object, I get the following error:

Error: Unknown property 'String.Address__c'

Any idea why? And how can I accomplish my goal of displaying this contact object field?

        <apex:repeat value="{!entities}" var="r">
            <tr>
              <td>{!r.Name}</td>
              <td>{!r.Billing_Contact__c.Address__c}</td>
              <td>{!r.Email_1__c}</td>
              <td>{!r.Phone_1__c}</td>
              <td><apex:outputfield value="{!r.Inactive__c}"></apex:outputfield></td>
              <td>{!r.CreatedBy.Name}</td>
          </tr>
         </apex:repeat>

Answer 1

Relationships need to be navigated with the "r" extension, e.g.

r.Billing_Contact__r.Address__c

The "c" is the field itself, which is just an ID (hence the error about String); the "r" is the relationship.