A salesperson obtains several listings by going door-to-door in a neighborhood and warning residents that property values will drop once members of minority groups begin moving into the neighborhood. This would be considered:

Blockbusting

Explanation:

Blockbusting is defined as a practice where agents persuade owners to sell properties at a lower price by creating fears that people of another race or class will enter the area and property prices will drop.

The properties are sold afterwards for higher prices, therefore the agent makes profit.

This is a tactic used in the United States by real estate agents to convince white people sell property at a cheap price by creating fear of minorities entering the neighbourhood