Let's first define the following terms:
Marketing: Marketing is the process of getting people interested in a business's product and/or service.
Consultancy: A professional practice that gives expert advice within a particular field, especially business.
A marketing consultancy is a practice who provides expert advice on client acquisition & marketing towards businesses.
At scale, this can be done in a pure “done with you” or a “done for you” format. The difference is in the clients performing the work themselves or having it done for them.
A real estate marketing consultancy is just an industry specific marketing consultancy.