Final answer:
To specialize in apartment locating, a sales agent should have competence in residential sales and leasing, which is directly related to finding residential properties for clients.
Step-by-step explanation:
If a sales agent wishes to specialize in apartment locating, the areas of real estate they should be competent in primarily include residential sales and leasing. This is because apartment locating directly involves finding suitable residential properties for clients, which could be for rent or for sale. Knowledge in commercial leasing may be beneficial to a certain extent, particularly if the agent deals with mixed-use buildings where commercial spaces might be present. However, industrial development and land appraisal are less directly related to residential apartments and may not be essential for specialization in this area.